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Delivery Ratio used in CEAP in the Upper Mississippi River Basin

Documentation on Delivery Ratio

used for CEAP Cropland Modeling for

Various River Basins

in the United States

Santhi Chinnasamy1, Xiuying Wang1, Jeff Arnold2, Jimmy Williams1, Mike White2, Narayanan

Kannan1and Mauro Diluzio1

1Texas AgriLife Research Blackland Research and Extension Center 720 East Blackland Road Temple, TX, 76502

2USDA-Agricultural Research Service Grassland Soil and Water Research Laboratory 802 East Blackland Road Temple, TX, 76502

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Chapter Organization

This document describes the delivery ratio procedure used in the CEAP National Assessment for Crop-

land. The delivery ratio is a factor that compensates for the natural attenuation or loss of sediment and

nutrients as they travel in water from the source to the watershed outlet. This document covers the deli-

very ratio procedure used in Soil and Water Assessment Tool (SWAT) and Agricultural Policy Extend-

er (APEX) models to account for deposition of sediment, nitrogen, phosphorus and atrazine in ditches,

floodplains, and tributary stream channels during transit from the edge of the field or HRUs to the 8-

digit watershed outlet. The document is arranged as follows: Chapter 1 covers the development of the

delivery ratio procedure in APEX and SWAT models and sediment delivery ratio estimated for the Up-

per Mississippi River basin with several illustrations of the sediment delivery ratio for various types of

readers/audience from field level to University researchers. Chapters 2 through 5 further describe the

delivery ratio used in other river basins of the United States by the order of completion. References

cited in all the Chapters are provided in the Reference Section in Chapter 1.

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Delivery Ratio used in CEAP Cropland Modeling in the Upper Mississippi River

Basin

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Background on Sedimentation and Sediment Delivery Ratio

Problems caused by soil erosion and sedimentation include losses of soil productivity, water quality degradation, and decreased capacity of channels and reservoirs. Sediment may carry pollutants into water systems and cause signifi-cant water quality problems. Erosion of soil and sediment yield, and subsequent nutrients and pesticides transported with sediment can be strongly impacted by land manage-ment practices, land use and climate changes (Clark et al., 1985). Policy makers need to quantify erosion rates and sediment yields at regional or global levels in order to eva-luate and develop environmental and land use management plans (e.g., COST634, 2005; Mausbach and Dedrick, 2004). The historical record of sediment data is sparse. For example, only a few sediment sampling stations exist in the United Sates and most of the stations have relatively short records (Pannell, 1999). Therefore, reasonable and realistic prediction of sediment yield is important for man-aging natural resources and protecting the environment.

The methods involving estimating sediment delivery ratios (e.g., Lim et al., 2005; Syvitski et al., 2005; Mutua et al., 2006; Bhattarai and Dutta, 2007) or calculating sediment transport capacity (e.g., Morgan et al., 1998; Van Rom-paey et al., 2001; Vente et at., 2007) are often used to link gross erosion to sediment yield at the watershed outlet. However, not all of the soil that erodes from fields ends up in the watershed outlet. Most of the soil that is eroded gets deposited on the way, although the deposition is tempo-rary. Eroded soil may deposit in low spots, on flatter lands, at the edge of the field and sometimes settles at the bottom of the channel. The delivery ratio is a factor that compen-sates for the natural attenuation or loss of sediment (and nutrients) as they travel in water from the source to the watershed outlet. The processes of transport of sediment from different sources, deposition and re-entrainment on the way to the mouth of a watershed are difficult to model without detailed topographic and small-scale intensive soils and surface condition data. The sediment delivery ratio (SDR) is used as a logical tool to integrate the factors that affect the production of sediment from the gross ero-sion occurring in a watershed. Traditionally, the SDR is defined as the ratio of sediment load delivered to the wa-tershed outlet (sediment yield) to gross erosion occurring from sources within the watershed. Types of erosion in-clude sheet, rill, wind, classic gully, ephemeral gully, streambank, streambed, roadbank and ditch, roadbed, con-

struction, landslides, and background or geologic erosion. SDR can be affected by a number of factors including hy-drological inputs (rainfall-runoff factors), landscape and watershed characteristics (e.g., land use/land cover, near-ness to the main stream, channel density, drainage area, slope, slope length), soil properties (sediment source, tex-ture) and their interactions. The amount of floodplain se-dimentation occurring and the presence of hydrologically controlled areas (such as ponds, reservoirs, lakes, wet-lands, etc.) also affect the rate of sediment delivery to the watershed mouth and hence the SDR. These complexities make the SDR regionalization mainly empirical. Numer-ous SDR relationships have been developed based on combinations of these factors (Ouyang and Bartholic, 1997). Sediment delivery ratios have also been developed based on measured rates of sediment accumulations in re-servoirs. The types of erosion occurring in a contributing watershed provide information on the relative SDR, when the measured sedimentation rates are also known.

Sediment delivery ratios are used mostly in planning small to medium water resources projects. Historically one of the most important applications was the NRCS flood con-trol program that involved planning, designing, and eva-luating flood water retarding structures. Traditionally, de-livery ratios have been estimated by comparing sediment yield data with predicted gross erosion. These delivery ratios have been related to watershed characteristics to de-velop delivery ratio prediction equations for use on un-gaged watersheds (Gottschalk and Brune 1950; Maner 1958; Maner 1962; Roehl 1962; Williams and Berndt 1972). However, these analyses depend on the existence of long periods of sediment yield records at the stream gaging stations and; therefore, were limited to a few re-gions of the United States because of insufficient data. This deficiency was partially overcome by using simulated sediment yields (Williams, 1977) for determining delivery ratios. Long-term average annual sediment yields are di-vided by gross erosion to calculate delivery ratios. These simulated delivery ratios are related to watershed characte-ristics to develop equations for predicting delivery ratios for nearby ungaged watersheds.

With the development of the Modified Universal Soil Loss Equation (MUSLE) (Williams 1975a) and sediment routing (Williams, 1975b; Williams, 1978) it became ap-parent that one of the most important variables in estimat-ing delivery ratios was the peak runoff rate (qp). The origi-nal sediment routing model (Williams 1975b) routed se-

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diment from subarea outlets to the watershed outlet as a function of qp

0.56, travel time, and median particle size. This concept is used in the Agricultural Policy Environ-mental eXtender (APEX) model (Williams and Izaurralde, 2006). Gassman et al. (2009) have provided a comprehen-sive review of APEX model applications and stated that APEX is one of the few existing models which is capable of simulating flow and pollutant transport routing at the field scale. The APEX model has been chosen as the field-scale modeling tool for the Conservation Effects Assess-ment Project (CEAP).

The CEAP was initiated to quantify the environmental benefits of conservation practices at the regional/national scale. In CEAP, the edge-of-field effects of the conserva-tion practices implemented on cultivated cropland and land enrolled in the Conservation Reserve Program (CRP) of the watershed were assessed using the field scale model, APEX. The watershed scale model, SWAT (Soil and Wa-ter Assessment Tool) was used to simulate the non-cultivated land including pasture, range, urban, forest and wetlands and point sources in the watershed. The results from the APEX model simulations were integrated into the regional water quality model—SWAT (Arnold, et al., 1998; Arnold, et al., 1999; Arnold and Fohrer, 2005)—to assess the off-site effects of conservation practices at re-gional level (Santhi et al., 2005). Gassman et al., (2007) have provided a comprehensive review of SWAT model applications across United States and other countries and recommended SWAT as one of the widely used watershed models with expanding modeling capabilities.

Databases and model inputs required for SWAT in CEAP is derived from a framework called, HUMUS (Hydrologic Unit Modeling of the United States). In HUMUS/SWAT system, each major river basin in the United States is treated as a watershed and each 8-digit watershed as a subwatershed or subbasin (Figure 1-1). At the 8-digit wa-tershed level, two simulation models, APEX and SWAT, were run independently. The cultivated area estimates were made via a sampling and APEX modeling approach. The simulated results (flow, sediment, nutrients and pesti-cides) from APEX were aggregated to the 8-digit wa-tershed using the statistical sampling weights derived from the National Resource Inventory (NRI) data. The delivery ratio and upland sediment yields were estimated separately for cultivated land and non-cultivated land uses. The inte-grated modeling results at the 8-digit watershed outlets were routed downstream through the stream network along with point sources in SWAT for estimating the offsite ef-

fects of conservation practices on water quality at the wa-tershed outlets.

Chapter 1 describes the SDR procedure used in APEX and HUMUS/SWAT models for the CEAP National Assess-ment in the Upper Mississippi River Basin. This chapter includes a discussion of the following:

1. Development of SDR procedure used for estimating sediment losses (deposition) from edge-of-field to 8-digit watershed outlet in APEX for cultivated cropland and CRP;

2. Development of SDR procedure used for estimating sediment losses (deposition) from non-cultivated crop-land HRUs to 8-digit watershed outlet in SWAT;

3. Application and validation of the SDR procedure in the Upper Mississippi River Basin; and

4. Delivery ratio of sediment bound (organic) and soluble nutrients and pesticides

For CEAP, at the 8-digit watershed level, there are typical-ly 20 plus NRI-CEAP points simulated with APEX. Each APEX simulation represents a fraction of the cultivated areas by statistical weights assigned to each point. There are about 30-40 hydrologic resource units (HRUs) simu-lated with SWAT. Each HRU represents a particular land use/soil combination, which is a portion of the 8-digit wa-tershed area and does not represent a contiguous land area. Therefore, both the APEX-simulated-cultivated land and SWAT-simulated-HRUs are assumed randomly distributed within the 8-digit watershed.

Both APEX and SWAT compute SDR as a function of the ratio of time of concentration of the field or HRU to the time of concentration of the 8-digit watershed. As pre-viously described, SDRs are typically defined as the ratio of sediment yield to erosion (soil loss). It is to be noted that delivery ratio estimated for the CEAP national as-sessment is different from the traditionally estimated SDR. In the CEAP national assessment, the SDRs are estimated within each simulation and defined as the ratio of edge-of-field sediment delivered to the 8-digit watershed outlet to the sediment load simulated at APEX sites or SWAT-simulated-HRUs. APEX and SWAT models estimate the sediment yield from the randomly distributed APEX sub-areas and SWAT HRUs to the outlet of the 8-digit wa-tershed or subbasin.

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Figure 1-1. Major River Basins and 8-digit watersheds in the United States

Development of delivery ratio from APEX sites to 8-digit watershed outlets The APEX modeling setup for CEAP used information from the NRI-CEAP Cropland Survey. The survey was conducted at a subset of NRI sample points which provide statistical samples representing the diversity of soils and other conditions on the landscape. Since each APEX simu-lation represents a fraction of the cultivated areas within an 8-digit watershed, the actual locations are not known and are assumed to be randomly distributed. Due to this limita-tion, the development of SDR in this study depends on the efficiency of the algorithm with a modest input parameter requirement. The SDR can be estimated as:

YSDR = B (1)

∑YS

where YB is the sediment yield at the basin outlet and YS is the sediment yield at the outlet of the APEX sites (or edge-of-field sites). The field surrounding each NRI sample point for modeling purposes, is assumed to be 16 ha, and may be broken into a maximum of four apex subareas, de-pending on the presence of buffer areas or grassed water-ways. Edge-of-field sediment yield (Y) can be estimated using a variation of MUSLE called MUST (MUSLE de-veloped from Theory (Williams 1995):

αY = 2.5×(Q× q p ) × K ×C × P × LS ×CFRG (2)

where Q is the runoff volume (mm), qp is the peak runoff rate (mm h-1) , K, C, P, and LS are the linear USLE fac-tors, CFRG is the coarse fragment factor and α is the ru-noff and peak runoff rate exponent, which is set as 0.5 in the original MUST equation (Williams 1995). The α can be smaller than 0.5 in developing the delivery ratio. YB can be calculated with Eq. 2 by areally weighting the linear USLE factors and Q, and estimating qp at the basin outlet. YS can be estimated for each of the APEX sites using ap-propriate values of the linear USLE factors, Q, and qp. The delivery ratio can be estimated by substituting these values into Eq. 1. Since the linear USLE factors and Q cancel, the delivery ratio for each APEX site can be estimated with the equation:

⎛ q ⎞α

SDRS = ⎜ pB ⎟ (3)⎜ ⎟q⎝ pS ⎠

where SDRS is the delivery ratio for the APEX sites, qpB is the peak runoff rate at the basin outlet (mm h-1), and qpS is

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the peak runoff rate at the outlet of the APEX sites (mm h-

1).

Since the APEX simulation results are passed to SWAT at the basin outlet, qpB is not known when APEX is running. However, the peak runoff rate is a function of runoff vo-lume and watershed time of concentration:

⎛ Q ⎞ qp = f ⎜⎜ ⎟⎟ (4)t⎝ c ⎠

Substituting the inverse of tc for qp (Q cancels) in Eq 3 yields:

⎛ t ⎞α

SDRS = ⎜⎜ cS ⎟⎟ (5)

t⎝ cB ⎠ where tcS is the time of concentration of the APEX site and tcB is the time of concentration of the basin. The times of concentration can be estimated with the Kirpich equation in the metric form:

L0.77

t = 0.0663 × (6)c 0.385S where L is the watershed length along the main stem from the outlet to the most distant point (km) and S is the main stem slope (m/m).

Substituting tcS and tcB calculated from Eq. 6 in Eq. 5 yields:

0.77 0.385⎛ ⎞α

⎛ L ⎞ ⎛ S ⎞⎜ S B ⎟SDRS = ⎜⎜ ⎟⎟ ×⎜⎜ ⎟⎟ (7)⎜ L S ⎟⎝ B ⎠ ⎝ S ⎠⎝ ⎠ where LB and SB are the 8-digit watershed basin channel length (km) and basin channel slope (m/m), respectively; LS and SS are the APEX watershed length (km) and slope (m/m), respectively. Theα was set to 0.2.

Description of the delivery ratio procedure developed within SWAT SWAT simulates the sediment yield from the non-cultivated land HRUs using the Modified Universal Soil Loss Equation developed by Williams et al. (1975a and 1975b; Williams et al., 1995):

0.56sed = 11.8 ⋅ (Q ⋅ q ⋅ area ) ⋅ K ⋅ C ⋅ P ⋅ LS ⋅ CFRG (12)surf peak hru USLE USLE USLE USLE

where sed is the sediment load on a given day (metric tons), Qsurf is the surface runoff volume (mm), qpeak is the peak runoff rate (m3/s), areahru is the area of the HRU (ha), KUSLE is the USLE soil erodibility factor, CUSLE is the USLE cover and management factor, PUSLE is the USLE support practice factor, LSUSLE is the USLE topographic

factor and CFRG is the coarse fragment factor (Neitsch et al., 2005). The area of each HRU for various land use classes may vary from a few hundred acres to several thousands of acres within each 8-digit watershed.

After estimating the sediment load for each HRU, a deli-very ratio is applied to determine the amount of sediment that reaches the 8-digit watershed (HUC) outlet from each HRU. In SWAT, SDR is estimated as a function of the time of concentration of HRU to the time of concentration of the HUC/8-digit watershed. Time of concentration is related to watershed characteristics such as slope, slope length, landscape characteristics and drainage area:

dr _ exp⎛ t ⎞ c,hruSDR = ⎜ ⎟ (13)⎜ ⎟t⎝ c,sub ⎠

where tc,hru is the time of concentration of HRU in hours, tc,sub is the time of concentration of the subbasin (8-digit HUC) in hours, typically more than 24 hours for most of the 8-digit watersheds, and dr exp is the delivery ratio ex-ponent parameter. Time of concentration of HRU and of 8-digit also varies across the 8-digit watersheds. For the CEAP national assessment, the delivery ratio exponent (dr exp) was set to 0.5 in SWAT. This parameter is similar to the peak runoff rate exponent (α ) used in the MUSLE.

Computation of time of concentration of subbasin/HUC The time of concentration is calculated by summing the overland flow time (the time it takes for flow from the most remote point in the subbasin to reach the channel) and the channel flow time (the time it takes for flow in the upstream channels to reach the outlet). Total time of con-centration is the sum of overland and channel flow times:

t c , sub = t + tch , sub (14) ov

where tc,sub is the time of concentration for a subbasin (hr), tov is the time of concentration for overland flow (hr), and tch,sub is the time of concentration for channel flow (hr).

Computation of time of concentration of overland flow Tributary channel characteristics related to the HRU such as average slope length (m), HRU slope steepness (m m-1) and Manning’s “n” values representing roughness coeffi-cient for overland flow are used in computing overland flow time of concentration:

0.6 0.6L ⋅ n t = slp (15)ov 0.318 ⋅ slp

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where Lslp is the average subbasin slope length (m), slp is the average slope of HRU in the subbasin (m m-1), and n is Manning’s roughness coefficient for the overland flow representing characteristics of the land surface with resi-due cover or tillage operations. Manning’s ”n” ranges from 0.01 to 0.60.

Computation of time of concentration of channel flow of subbasin The time of concentration for channel flow of the subbasin is computed as:

0.62 ⋅ L ⋅ n0.75

t = (16)ch,sub 0.125 0.375Sub _ area ⋅ slpch

where tch,sub is the time of concentration for channel flow (hr), L is the channel length from the most distant point to the subbasin/HUC outlet (km) or the longest tributary channel length, n is Manning’s roughness coefficient for the channel representing the characteristics of the channel (ranges from 0.025 through 0.100), Sub_area is the subba-sin/HUC area (km2), and slpch is the average slope of the longest tributary channel (m m-1).

Computation of time of concentration of the HRU The time of concentration of HRU is estimated using the following equation.

t c , hru = t ov + t ch , hru (17)

Computation of time of concentration of channel flow of HRU The time of concentration for channel flow of the HRU is computed as:

0.62 ⋅ L * hru _ prop ⋅ n0.75

t = (18)ch,hru 0.3750.125hru _ area ⋅ slpch

where, hru_prop is the proportion of the tributary channel length in hru. It is estimated by multiplying the longest tributary channel length by the ratio of hru area to subbasin area, and hru_area is the area of hru.

Equations 15 and 18 are used in computing time of con-centration for HRU as in shown in Eq. 17. Thus, Eqs. 14 and 17 are used in Eq. 12 to compute the SDR. Figure 1-2. depicts the schematic of sediment sources and delivery as modeled with HUMUS/SWAT for the CEAP Cropland National Assessment.

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Figure 1-2. Schematic of sediment sources and delivery as modeled with HUMUS/SWAT and APEX for the CEAP Crop-land National Assessment

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Application and validation of sediment routing ra-tio procedures The delivery ratio procedures described above have been applied to the CEAP national assessment study in the Up-per Mississippi River Basin (UMRB) (Figure 1-3). The UMRB covers about 190,000 square miles, including large parts of Illinois, Iowa, Minnesota, Missouri, and Wiscon-sin, and small areas of Indiana, Michigan, and South Da-kota. The total cultivated cropland and land enrolled in the CRP General Signup is about 52 percent of the total UMRB area. In most basins, the percent of CRP land is generally less. Most of the cultivated land is located in Iowa, Illinois and Wisconsin. A total of 131 8-digit water-sheds are in the UMRB. Within each 8-digit watershed, the percent cultivated cropland and CRP area ranges from 0 to 89 percent. A total of 5534 representative cultivated fields (3703 NRI-CEAP cropland points and 1831 CRP points) were setup to run using APEX. The statistical weights associated with each representative field range from 6 to 1,369 thousand acres. Nine out of 131 8-digit watersheds in the UMRB have no CEAP points. These nine 8-digit watersheds have zero or fewer than 3 percen-tage cultivated cropland. Non-cultivated land is distributed over 4 percent of the UMRB. Within each 8-digit wa-tershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 4452 HRUs are simulated in the Upper Mississippi River Basin.

Cultivated cropland and CRP Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratios also vary for each culti-vated cropland site simulated in an 8-digit watershed. Ex-amples of inputs and the corresponding estimated delivery ratios are listed in Table 1-1. Examples of delivery ratio distributions at the 8-digit watershed level are shown in Figure 1-4. The mean delivery ratios for each of the 8-digit watershed in the UMRB range from 0.30 to 0.46 (Figure 1-5 and Table 1-2).

Non-cultivated land Since the runoff, tributary channel characteristics, HRU areas, and HUC area vary, sediment yield and delivery ratio also vary for each non-cultivated HRU simulated in an 8-digit watershed. Example inputs used and correspond-ing time of concentrations and delivery ratios for non-cultivated land HRUs are shown for three 8-digit water-sheds in Central Minnesota, Central Iowa and Eastern Missouri near St. Louis (Table 1-3). Figure 1-6 depicts the

distribution of SDR of non-cultivated land HRUs in those three 8-digit watersheds. Sediment delivery ratio varied from 0.16 to 0.46 depending on the HRU area, slope, slope length, land use characteristics and soil characteristics.

Figure 1-7 depicts the SDR estimated for major non-cultivated landuses such as forest, urban land, pasture, range grass, hay and urban construction HRUs in each 8-digit watershed in the Upper Mississippi River Basin. Since the SWAT HRU areas are morewidely varied than the areas used in APEX simulation sites (16 ha), the SDR is also varied for some of the pasture, forest and urban land HRUs. Sediment delivery ratios were less for urban con-struction HRUs as their areas are relatively smaller. The MUSLE equation used in SWAT accounts for the area and thus, sediment load predicted by MUSLE per area is lower as HRU area increases. Figure 1-8 depicts the distribution of SDRs for pasture, range grasses, forest, urban and urban construction HRUs in the Upper Mississippi River Basin.

Table 1-4. shows the mean SDR, 10th percentile and 90th percentile for the non-cultivated land HRUs in all 8-digit watersheds in the Upper Mississippi River Basin. Spatial variation of mean SDR estimated for non-cultivated land HRUs in 8-digit watersheds in the Upper Mississippi River basin is shown in Figure 1-9. The mean delivery ratio va-ried from 0.24 to 0.43across the 8-digit watersheds.

Validation of sediment delivery ratios used in the Upper Mississippi River Basin Sediment delivery ratio was used in APEX and SWAT models to account for deposition of sediment in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the 8-digit watershed outlet. The SDRs were used to estimate the sediment losses or deposition from each of the cropland APEX simulation sites and non-cropland HRUs to the 8-digit watershed out-lets. The mean SDRs were calculated from the SDRs of APEX sites and SWAT HRUs within each 8-digit wa-tershed. The mean SDR varied from 0.24 through 0.43.

Meade et al. (1990) developed relationships for sediment yields in the UMRB as a function of drainage area and land use based on a study conducted before 1950. Based on Meade’s relationships, the SDR from the edge-of-fields to the 8-digit watershed outlets is approximately 0.3 to 0.4. Sediment delivery ratios estimated for the upland in the CEAP national assessment study are closer to the delivery ratio range suggested by Meade et al. (1990). This indi-cates that the sediment modeling from the CEAP national assessment study are reasonable.

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Delivery ratio used to compute transport of sediment attached nutrients and pesticides from cropland APEX sites to the 8-digit watershed outlets Sediment transported nutrients and pesticides are simu-lated using an enrichment ratio approach:

YNPB =YNPS × DR× ERTO (8)

where YNP is the nutrient or pesticide load and ERTO is the enrichment ratio (concentration of nutrient/pesticide in outflow from APEX sites divided by that at the basin out-let). The enrichment ratio is calculated by considering se-diment concentration in the equation:

2ERTO = b1 ×YSCb (9)

where YSC is the sediment concentration of the outflow from the APEX sites and b1 and b2 are parameters that can be determined by considering two points in Eq. 9. For the enrichment ratio to approach 1.0, the sediment concentration must be extremely high. Conversely, for the enrichment ratio to approach 1/SDR, the sediment concentration must be low. The simultaneous solution of Eq. 9 at the boundaries assuming that sediment concentrations range from 5x10-4 to 0.1 Mg m-3 gives:

b2 = log(SDR)/ 2.301 (10) b1 =1/ 0.1b2 (11)

Thus, the delivery ratios and enrichment ratios are used to transport sediment, nutrients, and pesticides from APEX sites to the basin outlet for input to SWAT.

Delivery ratio used to compute transport of sediment attached nutrients and pesticides from non-cultivated land HRUs to the 8-digit watershed outlets For non-cultivated land uses simulated within SWAT, or-ganic nitrogen, phosphorus and pesticide transported with sediment are calculated with a loading function developed by McElroy et al. (1976) and modified by Williams and Hann (1978) for application to individual runoff events. The basic concept of the loading function used in SWAT is identical to APEX. The loading function estimates the dai-ly organic N runoff loss from a HRU, based on the concen-tration of organic N or P in the top soil layer in the field or HRU, the sediment yield, and the enrichment ratio. The enrichment ratio (Menzel, 1980) is the concentration of organic nitrogen, phosphorus and pesticide transported with sediment to the main channel to the concentration in the soil surface layer at the field or HRU.

In addition to the SDR, the enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sedi-ment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field or HRU to the outlet (Menzel, 1980). The enrichment ratio was defined as the organic nitrogen, or-ganic phosphorus, and sediment attached pesticide concen-tration transported with sediment to the watershed outlet divided by their concentration at the edge-of-field. As se-diment is transported from the edge-of-field to the wa-tershed outlet, coarse sediments are deposited first, while more of the fine sediments that hold organic particles re-main in suspension enriching the organic concentrations delivered to the watershed outlet.

Thus, the edge of loadings of sediment bound nutrients (organic nitrogen and phosphorus) and pesticides delivered to the 8-digit watershed outlets account for the delivery losses based on the SDR and enrichment ratio simulated within APEX model and SWAT models.

Delivery ratio for soluble nutrients used from cropland and CRP from APEX Loads simulated by APEX for each survey point were ap-propriately weighted to develop a single aggregated load for all cultivated cropland within each 8-digit watershed. Sediment and particulate (organic) nutrients forms are sub-ject to delivery ratios appropriate to their relative source locations within the subbasin and distance to the SWAT subbasin outlet. This adjustment is performed within the APEX prior to the inclusion of APEX loads into SWAT. However, soluble nutrient and pesticide loading from APEX is excluded from this delivery ratio adjustment. To reconcile this discrepancy, delivery ratio for soluble con-stituents were applied to APEX loads within the SWAT model. In this way both soluble and particulate constitu-ents from cultivated cropland are treated with a delivery ratio. In order to fit the existing modeling framework, sep-arate delivery ratios for soluble constituents were needed. Development of delivery ratios for soluble nutrients and pesticides is difficult. In-stream interaction between so-luble and particulate fractions are complex and difficult to isolate, thus there are little research data upon which to base appropriate values. Soluble delivery ratios for APEX loads were derived from in-stream soluble nutrient and pesticide delivery as predicted by SWAT. The SWAT model predicts these losses within each river reach using the routines adapted from the QUAL2E model. The aver-age delivery ratios predicted by SWAT for a single reach

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segment in the UMRB were 0.97, 0.93 and 0.94 for nitrate, soluble phosphorus and soluble pesticide, respectively. Because they are derived from the SWAT model, soluble loads from non-cultivated areas are already subject to simi-lar reductions. Application of soluble delivery ratios en-sures equitable treatment of pollutants between APEX and SWAT. Individual delivery ratios were calculated using equations (12 to 14) as described below. These values typ-ically ranged from 0.80 to 0.98, indicating in general a higher delivery ratio for soluble as compared to particulate (organic) fractions.

Development of delivery ratios for soluble nutrients and pesticides is difficult. There is little existing research upon which to base appropriate values. Instream interaction be-tween soluble and particulate fractions make it difficult to isolate delivery ratios for each fraction from measured da-ta, yet in order to fit the existing modeling framework sep-arate delivery ratios are needed. Due to a lack of measured delivery ratios for soluble fractions in the literature, these data were derived from SWAT predictions. Delivery ra-tios applied to the monthly soluble loads from the APEX model were derived from SWAT predicted pollutant reten-tion by reach. The SWAT model predicts the loss of so-luble nutrient and pesticides within each reach due to in-stream processes. These predictions can be used to esti-mate a delivery ratio for soluble fractions for each reach in the model. The average delivery ratios predicted by SWAT for a single reach segment in the UMRB were 0.97, 0.93 and 0.94 for nitrate, soluble phosphorus and soluble pesticide, respectively. Because they are derived from the SWAT model, soluble loads from non-cultivated areas are already subject to similar reductions. To ensure equitable treatment of soluble pollutants between APEX and SWAT, the application of these delivery ratios is needed. Individu-al delivery ratios were calculated using Eq. 12 through 14 as described below. Delivery ratios used for soluble nu-trients and pesticides were greater than 0.9 in most of the basins.

Nitrate Delivery Ratio

The nitrate delivery ratio in the main channel reach, NO3_DR_RCH, is calculated as follows:

NO3_DR_RCH = NO3_OUT_RCH/ NO3_IN_RCH (12)

where NO3_IN_RCH is the nitrate transported with water into reach and NO3_OUT_RCH is the nitrate transported with water out of reach. NO3_IN_RCH load includes ni-trogen loads accumulated from subbasins above that reach).

Soluble Phosphorus Delivery Ratio

MINP_DR_RCH = MINP_OUT_RCH/ MINP_IN_RCH (13)

where, MINP_DR_RCH is the in-stream mineral phospho-rus delivery ratio in the main channel reach, MINP_IN_RCH is the mineral phosphorus transported with water into reach, and MINP_OUT_RCH is the miner-al phosphorus transported with water out of reach. MINP_IN load includes phosphorus loads accumulated from subbasins above that reach).

Soluble Pesticide Delivery Ratio

SOLPST_DR_RCH = SOLPST_OUT_RCH/ SOLPST_IN_RCH (14)

where, SOLPST_DR_RCH is the instream soluble pesti-cide delivery ratio in the main channel reach, SOLPST_IN_RCH is the soluble pesticide transported with water into reach, and SOLPST_OUT_RCH is the soluble pesticide transported with water out of reach.

While more than one pesticide may be applied to the HRUs in SWAT, due to the complexity of the pesticide equations only one pesticide is routed through the stream network. Several types of pesticides are applied to crop-land and horticultural land in the Upper Mississippi River Basin. For the CEAP national assessment, atrazine was chosen as one of the high priority or high risk pesticides in the Upper Mississippi River Basin. The only source of atrazine load is cultivated cropland; point sources and non-cultivated land had no atrazine contributions. Atrazine is routed through the stream reach during SWAT simulation. A delivery ratio of 0.94 was chosen soluble pesticides for the UMRB.

Summary • Sediment delivery ratio is used to account for the

sediment losses or deposition in ditches, channels, and floodplain occurring from edge-of-field of the cropland or non-cropland HRU to 8-digit wa-tershed outlets in each river basin.

• Sediment delivery ratio is unique for each culti-vated land and CRP survey point and each non-cultivated cropland HRU. Sediment delivery ratio varied as a function of drainage area, HRU of farm-field area, channel slope, slope length, soil, land use and management factors.

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• Mean SDR (from edge-of-field to 8-digit wa-tershed outlet SDR) varied from 0.3 to 0.5 for cul-tivated and CRP land simulated within APEX and it varied from 0.21 to 0.45 for non-cultivated land use HRUs simulated within SWAT.

• Edge-of-field loadings of sediment-bound nu-trients (organic nitrogen and phosphorus) deli-vered to the 8-digit watershed outlets account for the delivery losses based on the SDR and enrich-

ment ratio simulated within APEX and SWAT models.

• Soluble nutrient and pesticide delivery ratios were derived from the SWAT instream model and ap-plied to APEX loadings. The application of so-luble nutrient and pesticide delivery ratios to APEX loading ensures equitable treatment of the loads generated for cultivated and non-cultivated areas.

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Figure 1-3 Map of the 8-digit watersheds in the Upper Mississippi River Basin

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Figure 1-4 Examples of sediment delivery ratio distributions for cultivated cropland (edge-of-field to 8-digit wa-tershed outlet) in the Upper Mississippi River Basin

HUC=07020011 HUC=07040008 HUC=07060006 HUC=07120001 HUC=07140204

0.3

0.35

0.4

0.45

0.5

0.55

0.3

0.35

0.4

0.45

0.5

0.55

0.3

0.35

0.4

0.45

0.5

0.55

0.3

0.35

0.4

0.45

0.5

0.55

0.3

0.35

0.4

0.45

0.5

0.55

Figure 1-5 Mean sediment delivery ratio (sediment yield at the 8-digit watershed outlet divided by sediment yield at the edge-of-cropland fields) for cultivated cropland in the Upper Mississippi River Basin

Del

iver

y ra

tio d

istr

ibut

ion

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Table 1-1 Examples of inputs and estimated delivery ratios for cultivated cropland in the Upper Mississippi River Basin

8-digit wa-tershed NO.

SWAT basin

channel length

LB (km)

SWAT basin channel slope

SB (m/m)

APEX site watershed

length‡

LS (km)

APEX site main

stem slope SS (m/m)

Time of conc.

of the basin tcB (h)

Time of conc. of the APEX

site tcW (h)

Delivery ratio DRS

07100009 239.9 0.001 0.447 0.051 64.44 0.11 0.28 0.447 0.016 64.44 0.18 0.31 0.447 0.002 64.44 0.39 0.36

07020001 92.3 0.003 0.447 0.013 20.23 0.19 0.39 07070006 115.5 0.002 0.447 0.031 28.11 0.14 0.34 07010108 69.5 0.001 0.447 0.017 24.82 0.17 0.37

‡ Each APEX site is assumed to be a 16 ha of square area.

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Table 1-2 Sediment delivery ratios for cultivated cropland by 8-digit watershed

HUC Cropland CRP Crop + CRP

Points Mean SDR Points Mean

SDR Points Mean SDR

10th per-centile

90th percen-tile

7010104 4 0.38 4 0.38 0.34 0.49 7010106 8 0.37 3 0.36 11 0.37 0.34 0.41 7010107 5 0.39 2 0.37 7 0.39 0.37 0.40 7010108 5 0.39 14 0.38 19 0.38 0.36 0.43 7010201 10 0.42 1 0.37 11 0.41 0.36 0.53 7010202 13 0.35 9 0.34 22 0.35 0.32 0.39 7010203 16 0.39 4 0.36 20 0.38 0.34 0.47 7010204 25 0.37 30 0.37 55 0.37 0.33 0.40 7010205 24 0.39 3 0.37 27 0.39 0.34 0.49 7010206 11 0.40 11 0.40 0.37 0.44 7010207 18 0.41 18 0.41 0.36 0.50 7020001 41 0.41 38 0.39 79 0.40 0.37 0.43 7020002 10 0.41 6 0.39 16 0.40 0.35 0.50 7020003 35 0.44 23 0.41 58 0.43 0.37 0.55 7020004 35 0.39 24 0.36 59 0.38 0.33 0.44 7020005 31 0.37 36 0.36 67 0.37 0.32 0.46 7020006 17 0.42 17 0.40 34 0.41 0.37 0.48 7020007 24 0.43 3 0.40 27 0.42 0.36 0.51 7020008 32 0.37 4 0.37 36 0.37 0.33 0.40 7020009 38 0.38 2 0.32 40 0.38 0.32 0.46 7020010 17 0.45 4 0.41 21 0.44 0.39 0.50 7020011 30 0.39 10 0.35 40 0.38 0.33 0.45 7020012 34 0.36 6 0.32 40 0.36 0.31 0.41 7030001 3 0.37 3 0.37 0.33 0.44 7030003 1 0.33 1 0.33 0.33 0.33 7030004 7 0.35 7 0.35 0.32 0.37 7030005 28 0.34 17 0.33 45 0.34 0.30 0.37 7040001 35 0.40 13 0.37 48 0.39 0.35 0.45 7040002 76 0.36 30 0.34 106 0.35 0.31 0.44 7040003 20 0.34 11 0.33 31 0.34 0.31 0.37 7040004 62 0.36 16 0.33 78 0.35 0.31 0.38 7040005 13 0.34 13 0.32 26 0.33 0.31 0.37 7040006 9 0.38 7 0.34 16 0.36 0.34 0.41 7040007 14 0.34 3 0.29 17 0.33 0.28 0.37 7040008 85 0.36 40 0.33 125 0.35 0.31 0.41 7050001 1 0.33 1 0.33 0.33 0.33 7050002 1 0.39 1 0.39 0.39 0.39 7050004 1 0.44 1 0.41 2 0.43 0.41 0.44 7050005 23 0.36 6 0.33 29 0.35 0.31 0.38 7050006 5 0.35 2 0.33 7 0.34 0.31 0.38 7050007 20 0.35 16 0.33 36 0.34 0.30 0.36 7060001 17 0.42 34 0.38 51 0.40 0.37 0.43 7060002 34 0.35 32 0.32 66 0.33 0.31 0.37 7060003 26 0.38 35 0.36 61 0.37 0.35 0.40

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7060004 30 0.33 41 0.30 71 0.31 0.29 0.35 7060005 49 0.41 46 0.36 95 0.38 0.35 0.43 7060006 61 0.32 46 0.29 107 0.31 0.29 0.35 7070002 13 0.37 13 0.37 0.35 0.40 7070003 34 0.34 6 0.29 40 0.33 0.29 0.37 7070004 4 0.37 6 0.33 10 0.35 0.32 0.44 7070005 21 0.34 39 0.31 60 0.32 0.30 0.35 7070006 9 0.36 15 0.34 24 0.34 0.33 0.39 7080101 41 0.39 12 0.36 53 0.39 0.34 0.46 7080102 35 0.36 7 0.33 42 0.36 0.33 0.43 7080103 36 0.37 11 0.32 47 0.35 0.31 0.41 7080104 74 0.39 19 0.35 93 0.38 0.33 0.44 7080105 41 0.35 23 0.32 64 0.34 0.29 0.42 7080106 21 0.34 27 0.32 48 0.33 0.31 0.37 7080107 36 0.37 58 0.31 94 0.33 0.30 0.40 7080201 82 0.36 25 0.35 107 0.36 0.31 0.42 7080202 45 0.39 20 0.38 65 0.39 0.34 0.47 7080203 16 0.40 7 0.39 23 0.40 0.35 0.47 7080204 16 0.39 3 0.35 19 0.38 0.34 0.48 7080205 43 0.34 7 0.30 50 0.34 0.30 0.35 7080206 24 0.40 11 0.35 35 0.39 0.34 0.47 7080207 29 0.36 7 0.34 36 0.36 0.31 0.42 7080208 28 0.36 21 0.32 49 0.35 0.31 0.42 7080209 69 0.36 52 0.32 121 0.34 0.30 0.39 7090001 69 0.36 16 0.32 85 0.35 0.31 0.38 7090002 22 0.40 7 0.37 29 0.39 0.34 0.42 7090003 50 0.34 38 0.31 88 0.33 0.30 0.36 7090004 19 0.37 6 0.33 25 0.36 0.32 0.45 7090005 73 0.36 22 0.32 95 0.35 0.31 0.40 7090006 64 0.39 6 0.36 70 0.39 0.35 0.43 7090007 25 0.38 5 0.35 30 0.38 0.33 0.42 7100001 78 0.39 24 0.37 102 0.39 0.34 0.42 7100002 18 0.39 7 0.36 25 0.38 0.32 0.47 7100003 28 0.40 6 0.39 34 0.40 0.36 0.46 7100004 31 0.39 2 0.39 33 0.39 0.36 0.47 7100005 15 0.41 1 0.37 16 0.41 0.36 0.47 7100006 44 0.34 5 0.31 49 0.34 0.31 0.37 7100007 31 0.39 19 0.33 50 0.37 0.32 0.47 7100008 46 0.34 59 0.31 105 0.32 0.29 0.36 7100009 27 0.32 83 0.30 110 0.30 0.28 0.34 7110001 35 0.35 38 0.32 73 0.34 0.30 0.39 7110002 25 0.35 43 0.32 68 0.33 0.30 0.37 7110003 13 0.38 40 0.34 53 0.35 0.31 0.38 7110004 35 0.40 25 0.37 60 0.39 0.35 0.44 7110005 24 0.35 41 0.33 65 0.34 0.30 0.37 7110006 33 0.39 52 0.36 85 0.37 0.34 0.39

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7110007 19 0.40 29 0.38 48 0.39 0.36 0.42 7110008 30 0.36 15 0.33 45 0.35 0.32 0.39 7110009 21 0.41 6 0.37 27 0.40 0.35 0.47 7120001 71 0.38 4 0.32 75 0.38 0.33 0.43 7120002 56 0.41 4 0.37 60 0.41 0.35 0.48 7120003 3 0.46 3 0.46 0.40 0.50 7120004 15 0.41 3 0.39 18 0.41 0.37 0.45 7120005 26 0.41 2 0.35 28 0.41 0.35 0.47 7120006 41 0.34 9 0.33 50 0.34 0.30 0.37 7120007 49 0.39 2 0.34 51 0.38 0.34 0.46 7130001 53 0.35 1 0.31 54 0.35 0.32 0.36 7130002 38 0.40 3 0.40 41 0.40 0.36 0.48 7130003 35 0.42 6 0.40 41 0.42 0.37 0.47 7130004 22 0.37 6 0.33 28 0.36 0.32 0.40 7130005 54 0.35 6 0.32 60 0.35 0.30 0.39 7130006 33 0.36 1 0.35 34 0.36 0.32 0.41 7130007 21 0.42 1 0.34 22 0.41 0.36 0.48 7130008 26 0.43 7 0.37 33 0.42 0.34 0.51 7130009 39 0.37 1 0.32 40 0.37 0.33 0.42 7130010 41 0.37 4 0.32 45 0.37 0.32 0.40 7130011 66 0.39 12 0.35 78 0.38 0.34 0.43 7130012 24 0.37 4 0.33 28 0.37 0.32 0.42 7140101 24 0.42 3 0.36 27 0.41 0.36 0.47 7140103 4 0.38 4 0.38 0.36 0.43 7140105 30 0.40 20 0.35 50 0.38 0.34 0.48 7140106 47 0.36 48 0.34 95 0.35 0.31 0.41 7140107 5 0.41 9 0.36 14 0.38 0.34 0.44 7140108 18 0.45 19 0.37 37 0.41 0.36 0.53 7140201 40 0.38 4 0.33 44 0.37 0.33 0.42 7140202 45 0.38 17 0.35 62 0.37 0.33 0.43 7140203 31 0.40 12 0.36 43 0.39 0.35 0.44 7140204 50 0.36 4 0.37 54 0.36 0.32 0.42

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Figure 1-6 Examples of sediment delivery ratio distributions for non-cultivated land HRUs for three 8-digit watersheds in the Upper Mississippi River Basin

HUC=7030003 HUC=7100004 HUC=7110008 (Central Minnesota) (Central Iowa) (East Central Missouri)

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Figure 1-7 Sediment delivery ratio estimated for major non-cultivated land HRUs (Forest, Pasture, Range, Urban and Construction) in the Upper Mississippi River Basin

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Figure 1-7 Sediment delivery ratio estimated for major non-cultivated land HRUs (Forest, Pasture, Range, Urban and Construction) in the Upper Mississippi River Basin (Contd.)

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Figure 1-8 Distribution of sediment delivery ratio for forest, urban, pasture, range and construction HRUs in the Upper Mississippi River Basin

Distribution for Forest Deciduous Distribution for Urban Land Distribution for Pasture Land

Forest Deciduous Urban Land Pasture Land

100.0% maximum 0.68 99.5% 0.62 97.5% 0.51 90.0% 0.42 75.0% Quartile 0.35 50.0% Median 0.30 25.0% Quartile 0.26 10.0% 0.23 2.5% 0.19 0.5% 0.16 0.0% minimum 0.12

100.0% maximum 99.5% 97.5% 90.0% 75.0% quartile 50.0% median 25.0% quartile 10.0% 2.5% 0.5% 0.0% minimum

0.67 0.64 0.55 0.46 0.39 0.33 0.28 0.24 0.21 0.18 0.17

100.0% maximum 99.5% 97.5% 90.0% 75.0% quartile 50.0% median 25.0% quartile 10.0% 2.5% 0.5% 0.0% minimum

0.51 0.48 0.43 0.37 0.33 0.28 0.24 0.21 0.15 0.12 0.10

Moments for Forest Deciduous

Mean 0.31 Std Dev 0.08 Std Err Mean 0.00 upper 95% Mean 0.32 lower 95% Mean 0.31 N 848

Moments for Urban land

Mean Std Dev Std Err Mean upper 95% Mean lower 95% Mean N

0.34 0.08 0.00 0.35 0.33 521

Moments for Pasture land

Mean Std Dev Std Err Mean upper 95% Mean lower 95% Mean N

0.29 0.07 0.00 0.29 0.28 450

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Figure 1-8 Distribution of sediment delivery ratio for forest, urban and pasture land HRUs in the Upper Mississippi River Basin Continued.

Distribution for Range Grasses Distribution for Urban Construction

Range Grasses Urban Construction

100.0% Maximum 0.70 100.0% maximum 0.23 99.5% 0.70 99.5% 0.23 97.5% 0.53 97.5% 0.18 90.0% 0.48 90.0% 0.17 75.0% Quartile 0.42 75.0% quartile 0.16 50.0% Median 0.32 50.0% median 0.13 25.0% Quartile 0.25 25.0% quartile 0.10 10.0% 0.22 10.0% 0.09 2.5% 0.19 2.5% 0.08 0.5% 0.17 0.5% 0.08 0.0% Minimum 0.17 0.0% minimum 0.08 Moments for Range Grasses Moments for Construction

Mean 0.34 Mean 0.13 Std Dev 0.10 Std Dev 0.03 Std Err Mean 0.01 Std Err Mean 0.00 upper 95% Mean 0.35 upper 95% Mean 0.13 lower 95% Mean 0.32 lower 95% Mean 0.12 N 141 N 132

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Figure 1-9 Mean sediment delivery ratio computed for non-cultivated land HRUs in the 8-digit watersheds in the Upper Mississippi River Basin

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Table 1-3 Example inputs, time of concentration and sediment delivery ratio estimated for non-cultivated land HRUs in three 8-digit watersheds in the Upper Mississippi River Basin

HUC Landuse

Time of

conc. of

HRU

Time of

conc. of sub-basin

Delivery Ratio

Area (ha)

Subbasin Slope

Length (km)

Subba-sin

Chan-nel

Slope (%)

HRU Slope

%

HRU Slope

Length (m)

7030003 Forest Deciduous 3.75 44.84 0.29 8189.06 97.45 0.001 0.006 149.49 7030003 Forest Deciduous 5.36 46.24 0.34 9156.76 97.45 0.001 0.003 291.43 7030003 7.42 46.24 0.40 19020.22 97.45 0.001 0.003 291.43 7030003 Forest Deciduous 5.59 47.55 0.34 4438.21 97.45 0.001 0.002 430.65 7030003 Forest Deciduous 3.64 45.56 0.28 4613.28 97.45 0.001 0.004 220.9 7030003 Forest Deciduous 4.23 45.56 0.31 7154.59 97.45 0.001 0.004 220.9 7030003 Forest Deciduous 3.14 45.13 0.26 4286.86 97.45 0.001 0.005 178.18 7030003 Forest Deciduous 2.86 45.13 0.25 3162.41 97.45 0.001 0.005 178.18 7030003 Pasture 2.48 44.84 0.24 2806.13 97.45 0.001 0.006 149.49 7030003 Forest Deciduous 3.45 44.84 0.28 6871.12 97.45 0.001 0.006 149.49 7030003 Water 3.07 44.84 0.26 5225.95 97.45 0.001 0.006 149.49 7030003 Pasture 3.26 45.56 0.27 3070.57 97.45 0.001 0.004 220.9 7030003 Forest Deciduous 5.47 45.56 0.35 12834.84 97.45 0.001 0.004 220.9 7030003 Range Brush 3.48 46.24 0.28 1314.22 97.45 0.001 0.003 291.43 7030003 Forest Deciduous 5.81 46.24 0.35 11212.00 97.45 0.001 0.003 291.43 7030003 Evergreen Forest 6.25 46.24 0.37 13286.06 97.45 0.001 0.003 291.43

7030003 Non-forested wet-land 4.75 46.24 0.32 6446.94 97.45 0.001 0.003 291.43

7030003 Forest Deciduous 3.76 44.84 0.29 8210.15 97.45 0.001 0.006 149.49 7030003 Horticulture 2.41 45.56 0.23 63.49 97.45 0.001 0.004 220.9 7030003 Legume Hay 4.45 45.56 0.31 8140.74 97.45 0.001 0.004 220.9 7030003 Other Hay 3.31 45.56 0.27 3274.88 97.45 0.001 0.004 220.9 7030003 Pasture 4.56 45.56 0.32 8626.58 97.45 0.001 0.004 220.9

7030003 Pasture with ma-nure 2.43 45.56 0.23 125.58 97.45 0.001 0.004 220.9

7030003 Range Grass 5.39 45.56 0.34 12454.14 97.45 0.001 0.004 220.9 7030003 Forest Deciduous 7.46 45.56 0.41 22695.27 97.45 0.001 0.004 220.9 7030003 Forest Mixed 2.51 45.56 0.24 338.62 97.45 0.001 0.004 220.9 7030003 Urban 4.64 45.56 0.32 8984.70 97.45 0.001 0.004 220.9


7030003 Legume Hay with Manure 2.39 45.56 0.23 15.81 97.45 0.001 0.004 220.9

7030003 Other Hay with Manure 2.41 45.56 0.23 52.87 97.45 0.001 0.004 220.9

7030003 Urban Construction 0.34 43.40 0.09 277.87 97.45 0.001 0.15 6.73 7030003 Pasture 3.49 45.13 0.28 5757.54 97.45 0.001 0.005 178.18

7030003 Deciduous Forest 6.05 45.13 0.37 17695.35 97.45 0.001 0.005 178.18


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7030003 Deciduous Forest 4.08 46.24 0.30 3595.33 97.45 0.001 0.003 291.43 7030003 Deciduous Forest 4.95 45.56 0.33 10414.63 97.45 0.001 0.004 220.9 7030003 Barren 2.39 45.56 0.23 13.79 97.45 0.001 0.004 220.9


7030003 Deciduous Forest 3.69 46.24 0.28 2065.97 97.45 0.001 0.003 291.43

7100004 Urban 7.68 52.82 0.38 4867.44 97.5 0.001 0.002 430.65 7100004 Barren 8.36 56.49 0.39 344.09 97.5 0.001 0.001 839.55 7100004 Urban 11.31 56.49 0.45 4822.25 97.5 0.001 0.001 839.55 7100004 Deciduous Forest 8.25 49.62 0.41 11641.30 97.5 0.001 0.009 101.16 7100004 Range Grass 7.40 49.74 0.39 9810.96 97.5 0.001 0.008 113.31 7100004 Deciduous Forest 10.54 49.74 0.46 15780.72 97.5 0.001 0.008 113.31

7100004 Evergreen Forest 1.36 49.74 0.17 49.35 97.5 0.001 0.008 113.31

7100004 Urban 5.55 49.74 0.33 6500.42 97.5 0.001 0.008 113.31


7100004 Horticulture 1.92 50.11 0.20 251.88 97.5 0.001 0.006 149.49 7100004 Legume Hay 3.77 50.11 0.27 2901.51 97.5 0.001 0.006 149.49 7100004 Other Hay 2.40 50.11 0.22 867.17 97.5 0.001 0.006 149.49 7100004 Pasture 7.05 50.11 0.38 8509.06 97.5 0.001 0.006 149.49

7100004 Pasture with ma-nure 1.71 50.11 0.19 32.91 97.5 0.001 0.006 149.49

7100004 Range Grass 1.68 50.11 0.18 5.93 97.5 0.001 0.006 149.49 7100004 Urban 10.58 50.11 0.46 15124.34 97.5 0.001 0.006 149.49 7100004 Forested Wetland 4.38 50.11 0.30 3882.58 97.5 0.001 0.006 149.49

7100004 Legume Hay with Manure 1.68 50.11 0.18 9.80 97.5 0.001 0.006 149.49

7100004 Other Hay with Manure 1.69 50.11 0.18 15.54 97.5 0.001 0.006 149.49

7100004 Urban Construction 1.26 48.67 0.16 1282.71 97.5 0.001 0.15 6.73 7100004 Water 5.27 49.74 0.33 6020.68 97.5 0.001 0.008 113.31

7100004 Mixed Forest

1.46 49.90 0.17 0.94 97.5 0.001 0.007 128.86 7100004 Urban 7.75 49.90 0.39 10159.64 97.5 0.001 0.007 128.86 7110008 Pasture 3.28 57.89 0.24 8189.06 121.08 0.001 0.006 149.49 7110008 Pasture 4.68 58.18 0.28 9156.76 121.08 0.001 0.005 178.18 7110008 Deciduous Forest 5.43 58.18 0.31 19020.22 121.08 0.001 0.005 178.18 7110008 Pasture 3.52 57.39 0.25 4438.21 121.08 0.001 0.009 101.16 7110008 Deciduous Forest 4.30 57.39 0.27 4613.28 121.08 0.001 0.009 101.16 7110008 Pasture 4.77 59.29 0.28 7154.59 121.08 0.001 0.003 291.43 7110008 Horticulture 2.12 58.18 0.19 4286.86 121.08 0.001 0.005 178.18 7110008 Legume Hay 3.83 58.18 0.26 3162.41 121.08 0.001 0.005 178.18 7110008 Other Hay 7.40 58.18 0.36 2806.13 121.08 0.001 0.005 178.18 7110008 Pasture 5.41 58.18 0.31 6871.12 121.08 0.001 0.005 178.18 7110008 Pasture with Ma-

nure 2.10 58.18 0.19 5225.95 121.08 0.001 0.005 178.18

7110008 Deciduous Forest 8.34 58.18 0.38 3070.57 121.08 0.001 0.005 178.18 7110008 Urban 4.25 58.18 0.27 12834.84 121.08 0.001 0.005 178.18

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7110008 Forested Wetland 4.65 58.18 0.28 1314.22 121.08 0.001 0.005 178.18 7110008 Water 2.80 58.18 0.22 11212.00 121.08 0.001 0.005 178.18 7110008 Legume Hay with

Manure 1.97 58.18 0.18 13286.06 121.08 0.001 0.005 178.18

7110008 Other Hay with Manure

2.09 58.18 0.19 6446.94 121.08 0.001 0.005 178.18

7110008 Pasture 2.89 57.29 0.23 8210.15 121.08 0.001 0.01 91.4 7110008 Forest Deciduous 5.37 57.29 0.31 63.49 121.08 0.001 0.01 91.4 7110008 Pasture 3.20 58.18 0.23 8140.74 121.08 0.001 0.005 178.18 7110008 Forest Deciduous 3.76 58.18 0.25 3274.88 121.08 0.001 0.005 178.18 7110008 Pasture 3.70 57.68 0.25 8626.58 121.08 0.001 0.007 128.86 7110008 Forest Deciduous 5.88 57.68 0.32 125.58 121.08 0.001 0.007 128.86 7110008 Barren 1.67 57.68 0.17 12454.14 121.08 0.001 0.007 128.86 7110008 Urban 3.72 57.68 0.25 22695.27 121.08 0.001 0.007 128.86 7110008 Pasture 3.49 58.60 0.24 338.62 121.08 0.001 0.004 220.9 7110008 Pasture 2.17 57.39 0.19 8984.70 121.08 0.001 0.009 101.16 7110008 Forest Deciduous 4.06 57.39 0.27 10980.90 121.08 0.001 0.009 101.16 7110008 Forest Deciduous 4.59 57.89 0.28 15.81 121.08 0.001 0.006 149.49 7110008 Pasture 4.37 57.68 0.28 52.87 121.08 0.001 0.007 128.86 7110008 Range Brush 1.62 57.68 0.17 277.87 121.08 0.001 0.007 128.86 7110008 Range Grass 2.87 57.68 0.22 5757.54 121.08 0.001 0.007 128.86 7110008 Forest Deciduous 9.36 57.68 0.40 17695.35 121.08 0.001 0.007 128.86 7110008 Evergreen Forest 1.75 57.68 0.17 7838.74 121.08 0.001 0.007 128.86 7110008 Mixed Forest 1.63 57.68 0.17 3595.33 121.08 0.001 0.007 128.86 7110008 Urban 3.91 57.68 0.26 10414.63 121.08 0.001 0.007 128.86 7110008 Urban Construction 0.57 56.45 0.10 13.79 121.08 0.001 0.15 6.73 7110008 Pasture 3.16 57.89 0.23 7011.85 121.08 0.001 0.006 149.49 7110008 Forest Deciduous 3.54 57.89 0.25 2065.97 121.08 0.001 0.006 149.49 7110008 Urban 3.16 57.89 0.23 8189.06 121.08 0.001 0.006 149.49 7110008 Non-forested Wet-

land 1.77 57.89 0.18 9156.76 121.08 0.001 0.006 149.49

1-28


Table 1-4. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Upper Mississippi River Basin

HUC Subbasin

Number_of non-cropland HRUs simulated within SWAT Mean SDR

10th

Percentile SDR

90th

Percentile SDR

7010101 1 41 0.31 0.25 0.38 7010102 2 36 0.28 0.21 0.39 7010103 3 40 0.31 0.24 0.37 7010104 4 42 0.32 0.25 0.39 7010105 5 37 0.30 0.24 0.37 7010106 6 41 0.30 0.23 0.36 7010107 7 48 0.30 0.25 0.36 7010108 8 45 0.32 0.26 0.36 7010201 9 49 0.32 0.28 0.39 7010202 10 39 0.26 0.19 0.34 7010203 11 47 0.29 0.24 0.34 7010204 12 33 0.30 0.23 0.40 7010205 13 33 0.30 0.23 0.41 7010206 14 37 0.36 0.30 0.44 7010207 15 45 0.38 0.33 0.43 7020001 16 30 0.35 0.29 0.45 7020002 17 32 0.33 0.27 0.42 7020003 18 27 0.34 0.28 0.48 7020004 19 24 0.30 0.21 0.46 7020005 20 27 0.30 0.22 0.42 7020006 21 24 0.34 0.27 0.50 7020007 22 26 0.34 0.27 0.52 7020008 23 23 0.29 0.19 0.48 7020009 24 26 0.30 0.23 0.47 7020010 25 25 0.37 0.30 0.49 7020011 26 26 0.30 0.23 0.45 7020012 27 24 0.27 0.18 0.45 7030001 28 48 0.28 0.22 0.35 7030002 29 48 0.26 0.20 0.34 7030003 30 45 0.29 0.23 0.36 7030004 31 49 0.26 0.21 0.33 7030005 32 42 0.26 0.18 0.35 7040001 33 39 0.31 0.25 0.38 7040002 34 30 0.27 0.18 0.40 7040003 35 41 0.25 0.18 0.36 7040004 36 33 0.25 0.17 0.42 7040005 37 33 0.26 0.17 0.39 7040006 38 37 0.29 0.22 0.39 7040007 39 36 0.25 0.14 0.34 7040008 40 31 0.24 0.16 0.40 7050001 41 44 0.26 0.19 0.34 7050002 42 48 0.29 0.23 0.34 7050003 43 49 0.31 0.24 0.36

1‐29


7050004 44 44 0.28 0.21 0.33 7050005 45 33 0.28 0.19 0.38 7050006 46 37 0.27 0.19 0.36 7050007 47 39 0.25 0.18 0.37 7060001 48 40 0.34 0.30 0.39 7060002 49 41 0.24 0.17 0.33 7060003 50 34 0.31 0.25 0.39 7060004 51 27 0.24 0.15 0.38 7060005 52 41 0.30 0.25 0.38 7060006 53 23 0.25 0.15 0.49 7070001 54 51 0.26 0.18 0.32 7070002 55 36 0.29 0.22 0.37 7070003 56 28 0.28 0.17 0.42 7070004 57 42 0.26 0.19 0.34 7070005 58 37 0.25 0.17 0.34 7070006 59 40 0.26 0.19 0.34 7080101 60 35 0.30 0.24 0.38 7080102 61 25 0.27 0.17 0.44 7080103 62 24 0.28 0.19 0.46 7080104 63 24 0.31 0.22 0.48 7080105 64 24 0.27 0.16 0.43 7080106 65 30 0.27 0.19 0.39 7080107 66 25 0.28 0.19 0.47 7080201 67 21 0.28 0.17 0.44 7080202 68 23 0.32 0.23 0.42 7080203 69 22 0.32 0.22 0.47 7080204 70 22 0.31 0.21 0.46 7080205 71 24 0.27 0.16 0.40 7080206 72 22 0.35 0.26 0.44 7080207 73 22 0.29 0.18 0.45 7080208 74 19 0.30 0.19 0.48 7080209 75 22 0.29 0.19 0.44 7090001 76 31 0.28 0.20 0.41 7090002 77 36 0.32 0.25 0.40 7090003 78 31 0.24 0.16 0.35 7090004 79 44 0.26 0.19 0.33 7090005 80 33 0.25 0.16 0.37 7090006 81 34 0.29 0.22 0.39 7090007 82 26 0.29 0.21 0.46 7100001 83 24 0.32 0.24 0.49 7100002 84 25 0.29 0.19 0.43 7100003 85 23 0.34 0.26 0.50 7100004 86 26 0.31 0.22 0.44 7100005 87 23 0.32 0.23 0.46 7100006 88 23 0.25 0.15 0.46 7100007 89 29 0.28 0.20 0.40 7100008 90 37 0.26 0.17 0.33 7100009 91 40 0.24 0.15 0.32 7110001 92 35 0.27 0.19 0.39 7110002 93 45 0.26 0.19 0.33

1‐30


7110003 94 44 0.28 0.22 0.37 7110004 95 43 0.33 0.30 0.40 7110005 96 41 0.27 0.20 0.35 7110006 97 40 0.31 0.25 0.37 7110007 98 38 0.33 0.27 0.41 7110008 99 46 0.27 0.21 0.34 7110009 100 39 0.36 0.31 0.43 7120001 101 26 0.28 0.20 0.42 7120002 102 22 0.32 0.24 0.53 7120003 103 30 0.43 0.39 0.55 7120004 104 35 0.36 0.32 0.45 7120005 105 25 0.31 0.22 0.45 7120006 106 35 0.27 0.19 0.35 7120007 107 24 0.30 0.22 0.46 7130001 108 24 0.28 0.18 0.45 7130002 109 20 0.31 0.21 0.49 7130003 110 33 0.36 0.29 0.44 7130004 111 25 0.29 0.19 0.43 7130005 112 22 0.28 0.18 0.50 7130006 113 23 0.28 0.18 0.47 7130007 114 23 0.35 0.27 0.47 7130008 115 25 0.33 0.26 0.49 7130009 116 21 0.29 0.19 0.51 7130010 117 30 0.30 0.22 0.36 7130011 118 27 0.32 0.25 0.42 7130012 119 27 0.31 0.21 0.44 7140101 120 46 0.32 0.26 0.39 7140102 121 48 0.24 0.18 0.33 7140103 122 54 0.25 0.19 0.33 7140104 123 48 0.26 0.21 0.32 7140105 124 56 0.29 0.25 0.35 7140106 125 49 0.27 0.22 0.33 7140107 126 51 0.30 0.26 0.35 7140108 127 41 0.34 0.29 0.43 7140201 128 26 0.28 0.20 0.47 7140202 129 38 0.29 0.22 0.38 7140203 130 40 0.30 0.24 0.36 7140204 131 45 0.27 0.21 0.33

1‐31


References

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Gassman, P.W., J.R. Williams, X. Wang, A. Saleh, E. Osei, L. Hauck, C. Izaurralde, and J. Flowers. 2009. The Agricul-tural Policy Environmental Extender (APEX) Model: An emerging tool for landscape and watershed environmental analyses. Technical Report 09-TR 49. Center for Agricultural and Rural Development, Iowa State University, Ames, Iowa.

Gottschalk, L.C., and G.M. Brune. 1950. Sediment design criteria for the Missouri Basin loess hills. USDA, SCS TP-97.

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McElroy, A.D., S.Y. Chiu, J.W. Nebgen, A. Aleti, and F.W. Bennett. 1976. Loading functions for assessment of water pollution from nonpoint sources. Environ. Prot. Tech. Serv., EPA 600/2-76-151.

Maner, S.B. 1958. Factors affecting sediment delivery rates in the Red Hills physiographic area. Trans. AGU , Vol. 39, No 4, pp. 669-675.

Maner, S. B. 1962. Factors influencing sediment delivery ratios in the Blackland Prairie land resource area. USDA, SCS, Fort Worth, TX, 10pp.

Mausbach, J.M., and A.R. Dedrick. 2004. The length we go: Measuring environmental benefits of conservation practices in the CEAP. J. Soil and Water Conserv. 59(5): 96A.

Meade, R. H., T. Yuzyk, and T. Day. 1990. Movement and storage of sediment in rivers of the United States and Canada. Pp. 255-280 in The Geology of North America. W. H. Riggs (ed.). Geological Society of America. O-1. Chapter 11.

Menzel, R. G. 1980. Enrichment ratios for water quality modeling. P. 486-492. In W. G. Knisel (ed.) CREAMS. A field scale model for chemicals, runoff and erosion from agricultural management systems. U.S. Dept. of Agric. Conserv. Res. Rept. Mo. 26.

Mutua, B.M., A. Klik and W. Loiskandl. 2006. Modeling soil erosion and sediment yield at a catchment scale: The case of masinga catchment, Kenya. Land Degradation & Development. 17:557-570.

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Morgan, R.P.C., Quinton, J.N., Smith, R.E., Govers, G., Poesen, J.W.A., Auerswald, K., Chisci, G., Torri, D., Styczen, M.E., 1998. The European Soil Erosion Model (EUROSEM): a dynamic approach for predicting sediment transport form fields and small catchments. Earth Surface Processes & Landforms 23: 527-544.

Neitsch, S. L., J. G. Arnold, J. R. Kiniry, and J. R. Williams. 2005. Soil and Water Assessment Tool (Version 2005). Theoretical documentation. Grassland, Soil and Water Research Laboratory, USDA-ARS, Temple, TX 76502 and Blackland Research Center, Temple, TX 76502.

Ouyang, D. and J. Bartholic. 1997. Predicting sediment delivery ratio in Saginaw Bay Watershed. In The 22nd National Association of Environmental Professionals Conference Proceedings. May 19-23, 1997, Orlando, FL. pp 659-671.

Pannell, R. 1999. Sediment response to large-scale environmental change: the Upper Mississippi River, 1943-1996. M.S. Thesis. University of Wisconsin-Madison.

Roehl, J.W. 1962. Sediment source areas, delivery ratios, and influencing morphological factors. In Land Erosion, IAHS Publ. No. 59, pp 202-213.

Santhi, C., Kannan, N., Di Luzio, M., Potter, S.R., Arnold, J.G., Atwood, J.D., and Kellogg, R.L. 2005. An approach for estimating water quality benefits of conservation practices at the national level. In American Society of Agricultural and Biological Engineers (ASABE), Annual International Meeting, Tampa, Florida, USA, July 17–20, 2005 (Paper Number: 052043).

Syvitski, J.P.M., Vorosmarty, C.J., Kettner, A.J. and Green, P. 2005: Impact of humans on the flux of terrestrial sediment to the global coastal ocean. Science 308(5720): 376–80.

Van Rompaey, A.J.J., G. Verstraeten, K. Van Oost, G. Govers, J. Poesen. 2001. Modeling mean annual sediment yield using a distributed approach. Earth Surface Processes & Landforms 26:1221-1236.

Vente, J. D., J. Poesen, M. Arabkhedri and G. Verstraeten. 2007. The sediment delivery problem revisited. Progress in Physical Geography 31(2):155-178.

Williams, J.R. 1975a. Sediment yield prediction with universal equation using runoff energy factor. U. S. Dept. Agric. Agric. Res. Serv, ARS-S-40.

Williams, J.R. 1975b. Sediment routing for agricultural watersheds. Water Resour. Bull. 11(5), 965-974.

Williams, J.R. 1977. Sediment delivery ratios determined with sediment and runoff models. In: Erosion and Solid Matter Transport in Inland Waters, IAHS-AISH, Publ. No. 122, pp. 168-179.

Williams, J.R. 1978. A sediment yield routing model. Proceedings of the Specialty Conference on Verification of Mathe-matical and Physical Models in Hydraulic Engineering. ASCE: College Park, MD. 662-670.

Williams, J.R. and H.D. Berndt. 1972. Sediment yield computed with Universal Equation. Journal of the Hydraulics Div., ASCE, Vol. 98, No HY12, pp. 2087-2098.

Williams, J.R. and R.W. Hann. 1978. Optimal operation of large agricultural watersheds with water quality constraints. Texas Water Resources Institute, Texas A&M Univ., Tech. Rept. No. 96.

Williams, J. R. and R. C. Izaurralde. 2006. The APEX model. In Watershed Models, 437-482. Singh, V.P. and D.K. Fre-vert, eds. Boca Raton, FL: CRC Press, Taylor & Francis.

1-33

Chapter 2

Delivery Ratio used in CEAP Cropland Modeling in the Chesapeake Bay

Watershed

2-1

Delivery Ratio used in CEAP in the Chesapeake Bay Watershed

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nu-trients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009) in the Chesapeake Bay Watershed. APEX si-mulates all of the basic biological, chemical, hydrological, and meteorological processes of farming systems and their interactions. Soil erosion is simulated over time, including wind, sheet and rill erosion. The nitrogen, phosphorus, and carbon cycles are simulated, including chemical transfor-mations in the soil that affect their availability for plant growth or for transport from the field.

While the APEX model was used to simulate the culti-vated cropland and the SWAT model was used to simulate the non-cultivated cropland in the 8-digit watersheds (sub-basins) of the river basin. SWAT is a physical process model with a daily time step (Arnold and Fohrer 2005; Arnold et al. 1998; Gassman et al. 2007). The hydrologic cycle in the model is divided into two parts. The land phase of the hydrologic cycle, or upland processes, simu-lates the amount of water, sediment, nutrients, and pesti-cides delivered from the land to the outlet of each wa-tershed. The routing phase of the hydrologic cycle, or channel processes, simulates the movement of water, se-diment, nutrients, and pesticides from the outlet of the up-stream watershed through the main channel network to the watershed outlet.

In SWAT, each 8-digit watershed is divided into multiple Hydrologic Response Units (HRUs) that have homogene-ous land use, soil and slope. SWAT is used to simulate the fate and transport of water, sediment, nutrients, and pesti-cides from various non-cropland HRUs as described in Chapter 1.

Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the deposition is temporary. Eroded soil may deposit in low spots, flatr lands, at the edge of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary stream channels dur-ing transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National Assessment model-ing. The SDR used in this study is a function of the ratio of the time of concentration for the HRU (land uses other than cultivated cropland) or field (cultivated cropland) to the time of concentration for the watershed (8-digit HUC).

The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to the time the surface water runoff reaches the outlet of the watershed. It is calculated by summing the overland flow time (the time it takes for flow from the remotest point in the watershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream channels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concentration for the HRU is derived from characteristics of the watershed, the HRU, and the propor-tion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique deli-very ratio within each watershed, as does each HRU. The description of the SDR procedure is provided in Chapter 1.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE de-veloped from Theory) (Williams 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to de-termine the amount of sediment that reaches the 8-digit watershed outlet from each APEX simulation site. The sediment load from APEX simulation sites are aggregated for the 8-digit watershed and integrated into the SWAT model at each 8-digit watershed to estimate the water qual-ity effects of conservation practices. In SWAT, the sedi-ment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimating the SDR for each HRU, the SDR is applied to determine the amount of sediment that reaches the 8-digit watershed out-let.

Sediment delivery ratios were estimated to account for sediment losses or deposition occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated cropland and CRP and non-cropland HRUs in the Chesapeake Bay Watershed (Figure 2-1). The Chesapeake Bay has a drainage area of 43.85 million acres. The cultivated cropland and land enrolled in the CRP General Signup is about 10 percent of the Chesapeake Bay Watershed. A total of 58 8-digit wa-tersheds are in the Chesapeake Bay Watershed (Figure 2-1). Within each 8-digit watershed, the percent of cultivated cropland and CRP area and non-cultivated cropland area varies widely across the entire watershed.

A total of 832 representative cultivated fields (771 NRI-CEAP cropland points and 61 CRP points) were setup to run using APEX. Eight out of 57, 8-digit watersheds in the Chesapeake Bay Watershed have no CEAP points.

2-2

Delivery Ratio used in CEAP in the Chesapeake Bay Watershed

These 8-digit watersheds have zero or fewer than 6% per-centage cultivated cropland.

Non-cultivated land is distributed over 90 percent of the Chesapeake Bay Watershed. Within each 8-digit wa-tershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 2598 HRUs are simulated in SWAT for the Chesapeake Bay Watershed.

Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each culti-vated cropland site simulated in an 8-digit watershed as well as for HRU. The number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit water-sheds in the Chesapeake Bay are shown in Table 2-1 and Figure 2-1. Table 2-2 shows the number of HRUs and mean, 10th percentile and 90th percentile of the SDRs es-timated for the non-cultivated land HRUs in the 8-digit watersheds in the Chesapeake Bay Watershed (Figure 2-1). The mean, 10th and 90th percentile SDRs for the non-cropland HRUs are depicted in Figure 2-2.

In addition to the SDR, an enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sedi-ment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge-of-field to the outlet. The enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed outlet as dicussed in Chapter 1. The enrichment ratio is esti-mated for each APEX simulation site and SWAT HRU and it varies from 0.5 to 1.5 (average=1). As sediment is transported from the edge-of-field to the watershed outlet, coarse sediments are deposited first while more of the fine sediment that hold organic particles remain in suspension, thus enriching the organic concentrations delivered to the watershed outlet.

A separate delivery ratio is used to simulate the transport of nitrate-nitrogen, soluble phosphorus, and soluble pesti-cides. In general, the proportion of soluble nutrients and pesticides delivered to rivers and streams is higher than the proportion attached to sediments because they are not sub-ject to sediment deposition.

2-3

Figure 2-1 Map of the 8-digit watersheds in the Chesapeake Bay Watershed

3-1

Table 2-1. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Chesapeake Bay Watershed

HUC Cropland CRP Crop + CRP Point

s Mean

SDR

Point s

Mean

SDR

Point s

Mean_S DR

10th percen-tile SDR

90th per-centile SDR

2050101 3 0.32 3 0.32 0.31 0.35 2050102 4 0.36 2 0.33 6 0.35 0.31 0.44 2050103 1 0.42 1 0.42 0.42 0.42 2050104 4 0.39 4 0.39 0.35 0.44 2050105 4 0.44 3 0.38 7 0.42 0.37 0.53 2050106 4 0.37 6 0.34 10 0.35 0.33 0.38 2050107 7 0.37 7 0.35 14 0.36 0.32 0.44 2050201 1 0.33 1 0.33 0.33 0.33 2050203 1 0.39 1 0.39 0.39 0.39 2050204 3 0.46 1 0.39 4 0.44 0.39 0.54 2050205 2 0.39 2 0.39 0.38 0.40 2050206 15 0.37 2 0.34 17 0.36 0.33 0.41 2050301 21 0.37 2 0.34 23 0.37 0.34 0.41 2050302 3 0.47 1 0.39 4 0.45 0.39 0.56 2050303 3 0.38 3 0.38 0.36 0.40 2050304 9 0.35 2 0.32 11 0.34 0.31 0.42 2050305 38 0.38 2 0.35 38 0.38 0.36 0.41 2050306 92 0.34 94 0.34 0.32 0.38 2060002 57 0.44 9 0.40 66 0.43 0.39 0.50 2060003 24 0.41 24 0.41 0.37 0.50 2060004 2 0.46 2 0.46 0.46 0.46 2060005 53 0.44 3 0.42 56 0.44 0.38 0.50 2060006 20 0.35 20 0.35 0.31 0.42 2060007 12 0.49 1 0.46 13 0.49 0.44 0.58 2060008 57 0.45 1 0.37 58 0.45 0.39 0.49 2060009 30 0.42 30 0.42 0.40 0.48 2060010 23 0.53 1 0.51 24 0.53 0.46 0.58 2070001 4 0.42 4 0.42 0.39 0.49 2070002 1 0.40 1 0.40 0.40 0.40 2070003 1 0.37 1 0.21 2 0.29 0.21 0.37 2070004 36 0.35 1 0.34 37 0.35 0.33 0.37 2070005 9 0.36 9 0.36 0.34 0.40 2070006 3 0.38 3 0.38 0.38 0.39 2070007 6 0.45 6 0.45 0.41 0.55 2070008 15 0.39 4 0.33 19 0.38 0.35 0.48 2070009 38 0.40 1 0.42 39 0.40 0.37 0.42 2070010 4 0.38 4 0.38 0.36 0.41 2070011 25 0.41 2 0.31 27 0.40 0.37 0.44 2080102 21 0.47 1 0.32 22 0.47 0.42 0.54 2080103 7 0.42 1 0.30 8 0.40 0.30 0.47 2080104 25 0.37 3 0.21 28 0.35 0.24 0.40

3-2

Sedi

men

t Del

iver

y R

atio

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

2080105 16 0.39 1 0.22 17 0.38 0.32 0.41 2080106 8 0.40 8 0.40 0.35 0.48 2080107 3 0.46 3 0.46 0.45 0.49 2080109 17 0.61 17 0.61 0.54 0.71 2080110 13 0.55 13 0.55 0.48 0.63 2080206 15 0.43 2 0.25 17 0.41 0.25 0.53 2080207 2 0.36 1 0.21 3 0.31 0.21 0.38 2080208 9 0.47 9 0.47 0.43 0.54

Figure 2-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed out-let by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Chesapeake Bay Watershed

Chesapeake Bay Watershed

0.8 Mean SDR 10th Percentile SDR 90th Percentile SDR

2050

101

2050

103

2050

105

2050

107

2050

203

2050

205

2050

301

2050

303

2050

305

2060

002

2060

004

2060

006

2060

008

2060

010

2070

002

2070

004

2070

006

2070

008

2070

010

2080

102

2080

104

2080

106

2080

109

2080

206

2080

208

HUC8

3-3

Table 2-3. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit water-sheds in the Chesapeake Bay Watershed

HUC Subbasin Number of non-cropland HRUs

simulated within SWAT

Mean SDR 10th Percen-tile

SDR

90th Percentile SDR

2050101 1 53 0.18 0.13 0.31 2050102 2 50 0.21 0.15 0.27 2050103 3 54 0.23 0.19 0.29 2050104 4 50 0.24 0.19 0.30 2050105 5 43 0.25 0.19 0.31 2050106 6 49 0.22 0.15 0.29 2050107 7 43 0.23 0.16 0.32 2050201 8 40 0.22 0.14 0.33 2050202 9 31 0.27 0.18 0.38 2050203 10 33 0.24 0.15 0.37 2050204 11 31 0.27 0.19 0.42 2050205 12 34 0.26 0.18 0.36 2050206 13 47 0.22 0.15 0.29 2050301 14 41 0.23 0.17 0.34 2050302 15 27 0.30 0.22 0.40 2050303 16 42 0.22 0.15 0.31 2050304 17 37 0.22 0.11 0.33 2050305 18 51 0.24 0.19 0.30 2050306 19 61 0.22 0.19 0.27 2060001 20 21 0.42 0.35 0.50 2060002 21 36 0.32 0.23 0.43 2060003 22 58 0.26 0.23 0.32 2060004 23 33 0.36 0.31 0.43 2060005 24 38 0.31 0.23 0.41 2060006 25 52 0.21 0.15 0.28 2060007 26 35 0.42 0.34 0.50 2060008 27 33 0.32 0.25 0.43 2060009 28 41 0.30 0.24 0.35 2060010 29 40 0.25 0.18 0.32 2070001 30 38 0.24 0.16 0.34 2070002 31 38 0.25 0.19 0.33 2070003 32 42 0.23 0.16 0.34 2070004 33 58 0.22 0.17 0.30 2070005 34 71 0.20 0.15 0.27 2070006 35 60 0.24 0.19 0.31 2070007 36 34 0.31 0.24 0.35 2070008 37 76 0.24 0.19 0.28 2070009 38 73 0.25 0.21 0.29 2070010 39 61 0.26 0.21 0.29 2070011 40 48 0.30 0.26 0.35 2080102 41 48 0.40 0.35 0.50

3-4

Sedi

men

t Del

iver

y R

atio

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

2080103 42 61 0.28 0.23 0.32 2080104 43 47 0.25 0.19 0.33 2080105 44 49 0.26 0.22 0.31 2080106 45 56 0.27 0.22 0.31 2080107 46 33 0.39 0.34 0.46 2080108 47 28 0.52 0.45 0.61 2080109 48 26 0.57 0.53 0.64 2080110 49 40 0.26 0.19 0.35 2080201 50 48 0.21 0.13 0.29 2080202 51 47 0.24 0.19 0.32 2080203 52 61 0.21 0.16 0.27 2080204 53 57 0.24 0.19 0.30 2080205 54 50 0.28 0.24 0.32 2080206 55 51 0.33 0.28 0.39 2080207 56 54 0.25 0.20 0.30 2080208 57 39 0.36 0.32 0.41

Figure 2-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed out-let by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit wa-tersheds in the Chesapeake Bay Watershed

Chesapeake Bay Watershed


2050

101

2050

103

2050

105

2050

107

2050

202

2050

204

2050

206

2050

302

2050

304

2050

306

2060

002

2060

004

2060

006

2060

008

2060

010

2070

002

2070

004

2070

006

2070

008

2070

010

2080

102

2080

104

2080

106

2080

108

2080

110

2080

202

2080

204

2080

206

2080

208

HUC8

3-5

Chapter 3

Delivery Ratio used in CEAP Cropland Modeling in the Delaware River Basin

3-6

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nutrients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009) in the Dela-ware River Basin. APEX simulates all of the basic biological, chemical, hydrological, and meteorologi-cal processes of farming systems and their interac-tions. Soil erosion is simulated over time, including wind, sheet and rill erosion. The nitrogen, phospho-rus, and carbon cycles are simulated, including chem-ical transformations in the soil that affect their availa-bility for plant growth or for transport from the field.

While the APEX model was used to simulate the cultivated cropland, the SWAT model was used to simulate the non-cultivated cropland in the 8-digit watersheds of the river basin. SWAT is a physical process model with a daily time step (Arnold and Fohrer 2005; Arnold et al. 1998; Gassman et al. 2007). The hydrologic cycle in the model is divided into two parts. The land phase of the hydrologic cycle, or upland processes, simulates the amount of water, sediment, nutrients, and pesticides delivered from the land to the outlet of each watershed. The routing phase of the hydrologic cycle, or channel processes, simulates the movement of water, sedi-ment, nutrients, and pesticides from the outlet of the upstream watershed through the main channel net-work to the watershed outlet.

In SWAT, each 8-digit watershed is divided into mul-tiple Hydrologic Response Units (HRUs) that have homogeneous land use, soil, and slope. SWAT is used to simulate the fate and transport of water, sedi-ment, nutrients, and pesticides from various non-cropland HRUs as described in Chapter 1.

Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the depo-sition is temporary. Eroded soil may deposit in lower spots, flatter lands, deposited at the edge of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary stream channels during transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National Assessment modeling. The SDR used in this study is a function of the ratio of the time of concentration for the HRU (land uses other than cultivated cropland) or

field (cultivated cropland) to the time of concentra-tion for the watershed (8-digit HUC). The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to the time the surface water runoff reaches the outlet of the watershed. It is calcu-lated by summing the overland flow time (the time it takes for flow from the remotest point in the wa-tershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream chan-nels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concen-tration for the HRU is derived from characteristics of the watershed, the HRU, and the proportion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique deli-very ratio within each watershed, as does each HRU. The description of the SDR procedure is provided in Chapter 1.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE developed from Theory) (Williams 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to determine the amount of sediment that reach the 8-digit watershed outlet from each APEX simulation site. The sediment load from apex simulation sites are aggregated for the 8-digit wa-tershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality effects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimat-ing the SDR for each HRU, the SDR is applied to determine the amount of sediment that reach the 8-digit watershed outlet.

Sediment delivery ratios were estimated to account for sediment losses or deposition occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated crop-land and CRP and non-cropland HRUs in the Dela-ware River Basin (Figure 3-1). The Delaware River Basin has a drainage area of 8.72 million acres. The cultivated cropland and land enrolled in the CRP General Signup is about 13 percent of the Delaware River Basin. A total of 13, 8-digit watersheds are in the Delaware River Basin (Figure 3-1). Within each 8-digit watershed, the percent of cultivated cropland and CRP area and non-cultivated cropland area varies widely across the entire watershed.

3-7

Delivery Ratio used in CEAP in the Delaware River Basin

A total of 188 representative cultivated fields (186 NRI-CEAP cropland points and 2 CRP points) were setup to run using APEX. Four out of 14, 8-digit wa-tersheds in the Delaware River Basin have no CEAP points. The non-cultivated land is distributed over 87 percent of the Chesapeake Bay Watershed. Within each 8-digit watershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construc-tion, barren land wetland and water are simulated as HRUs in SWAT. A total of 501 HRUs are simulated in SWAT for the Delaware River Basin.

Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each cultivated cropland site simulated in an 8-digit watershed and so as for HRU. The number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit watersheds in the Che-sapeake Bay are shown in Table 3-1 and Figure 3-2. Table 3-2 shows number of HRUs and mean, 10th percentile and 90th percentile of the SDRs estimated for the non-cultivated land HRUs in the 8-digit water-sheds in the Chesapeake Bay Watershed (Figure 3-2). The mean, 10th and 90th percentile SDRs for the non-cropland HRUs are plotted in Figure 3-3.

In addition to the SDR, an enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sediment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the outlet. The enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed outlet. The enrichment ratio is estimated for each APEX simula-tion site and SWAT HRUs and it varies from 0.5 to 1.5 (Average 1). As sediment is transported from the edge-of-field to the watershed outlet, coarse sedi-ments are deposited first while more of the fine sedi-ment that hold organic particles remain in suspension, thus enriching the organic concentrations delivered to the watershed outlet.

A separate delivery ratio is used to simulate the transport of nitrate nitrogen, soluble phosphorus, and soluble pesticides. In general, the proportion of so-luble nutrients and pesticides delivered to rivers and streams is higher than the proportion attached to se-diments because they are not subject to sediment de-position.

3-8


Figure 3-1 Map of the 8-digit watersheds in the Delaware River Basin

3-9


Table 3-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit water-sheds in the Delaware River Basin

HUC Subbasin Number of non-cropland HRUs simu-lated within

SWAT

Mean SDR 10th Percentile SDR

90th Percentile SDR

2040101 1 42 0.21 0.13 0.31 2040102 2 32 0.23 0.12 0.34 2040103 3 44 0.24 0.17 0.34 2040104 4 52 0.20 0.12 0.29 2040105 5 43 0.35 0.31 0.41 2040106 6 38 0.23 0.16 0.31 2040201 7 35 0.32 0.25 0.38 2040202 8 44 0.31 0.26 0.37 2040203 9 53 0.21 0.16 0.28 2040204 10 3 0.80 0.71 0.95 2040205 11 42 0.29 0.23 0.33 2040206 12 38 0.32 0.27 0.36 2040207 13 35 0.42 0.38 0.48 2040301 14 51 0.20 0.13 0.27 2040302 15 33 0.22 0.11 0.34

Figure 3-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed out-let by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit wa-tersheds in the Delaware River Basin

Delaware Bay Watershed

0.0 0.1 0.2 0.3 0.4 0.5

0.6 0.7 0.8 0.9 1.0

2040

101

2040

102

2040

103

2040

104

2040

105

2040

106

2040

201

2040

202

2040

203

2040

204

2040

205

2040

206

2040

207

HUC8

Sedi

men

t Del

iver

y R

atio

Mean SDR 10th Percentile SDR 90th Percentile SDR

3-10

Chapter 4

Delivery Ratio used in CEAP Cropland Modeling in the Ohio-Tennessee

River Basin

4-1

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nutrients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009) in the Ohio-Tennessee River Basin. APEX simulates all of the basic biological, chemical, hydrological, and meteo-rological processes of farming systems and their inte-ractions. Soil erosion is simulated over time, includ-ing wind erosion, sheet and rill erosion. The nitrogen, phosphorus, and carbon cycles are simulated, includ-ing chemical transformations in the soil that affect their availability for plant growth or for transport from the field.

While the APEX model was used to simulate the cultivated cropland, the SWAT model was used to simulate the non-cultivated cropland in the 8-digit watersheds of the river basin. SWAT is a physical process model with a daily time step (Arnold and Fohrer 2005; Arnold et al. 1998; Gassman et al. 2007). The hydrologic cycle in the model is divided into two parts. The land phase of the hydrologic cycle, or upland processes, simulates the amount of water, sediment, nutrients, and pesticides delivered from the land to the outlet of each watershed. The routing phase of the hydrologic cycle, or channel processes, simulates the movement of water, sedi-ment, nutrients, and pesticides from the outlet of the upstream watershed through the main channel net-work to the watershed outlet.

In SWAT, each 8-digit watershed is divided into mul-tiple Hydrologic Response Units (HRUs) that have homogeneous land use, soil and slope. SWAT is used to simulate the fate and transport of water, sediment, nutrients, and pesticides from various non-cropland HRUs as described in Chapter 1.

Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the depo-sition is temporary. Eroded soil may deposit in lower spots, flatter lands, deposited at the edge of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary stream channels during transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National Assessment modeling. The SDR used in this study is a function of the ratio of the time of concentration for

the HRU (land uses other than cultivated cropland) or field (cultivated cropland) to the time of concentra-tion for the watershed (8-digit HUC). The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to the time the surface water runoff reaches the outlet of the watershed. It is calcu-lated by summing the overland flow time (the time it takes for flow from the remotest point in the wa-tershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream chan-nels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concen-tration for the HRU is derived from characteristics of the watershed, the HRU, and the proportion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique deli-very ratio within each watershed, as does each HRU. The description of the SDR procedure is provided in Chapter 1.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE developed from Theory) (Williams 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to determine the amount of sediment that reach the 8-digit watershed outlet from each APEX simulation site. The sediment load from apex simulation sites are aggregated for the 8-digit wa-tershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality effects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimat-ing the SDR for each HRU, the SDR is applied to determine the amount of sediment that reach the 8-digit watershed outlet.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE developed from Theory) (Williams 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to determine the amount of sediment that reach the 8-digit watershed outlet from each APEX simulation site. The sediment load from apex simulation sites are aggregated for the 8-digit wa-tershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality effects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimat-

4-2

Delivery Ratio used in CEAP in the Ohio-Tennessee River Basin

ing the SDR for each HRU, the SDR is applied to determine the amount of sediment that reach the 8-digit watershed outlet.

Sediment delivery ratios were estimated to account for sediment losses occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated cropland and CRP and non-cropland HRUs in the Ohio-Tennessee River Basin (Figure 4-1). The Ohio-Tennessee River Basin has a drainage area of 130.39 million acres. The cul-tivated cropland and land enrolled in the CRP Gener-al Signup is about 21 percent of the Ohio-Tennessee River Basin. A total of 152 8-digit watersheds are in the Ohio-Tennessee River Basin (Figure 4-1). Within each 8-digit watershed, the percent of cultivated crop-land and CRP area and non-cultivated cropland area varies widely across the entire basin.

A total of 2465 representative cultivated fields (1989 NRI-CEAP cropland points and 476 CRP points) were setup to run using APEX. Twenty-six out of 120, 8-digit watersheds in the Ohio River basin have no CEAP points. The twenty-six 8-digit watersheds have zero or fewer than 10% percentage cultivated cropland. A total of 218 representative cultivated fields (135 NRI-CEAP cropland points and 83 CRP points) were setup to run using APEX. Eleven out of 32, 8-digit watersheds in the Tennessee River Basin have no CEAP points. The eleven 8-digit watersheds have zero or fewer than 3% percentage cultivated cropland.

Non-cultivated land is distributed over 79 percent of the Ohio-Tennessee River Basin. Within each 8-digit watershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 6574 HRUs are simulated in SWAT for the Ohio-Tennessee River Basin.

Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each cultivated cropland site simulated in an 8-digit watershed and so as for HRU. The number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit watersheds in the Ohio-Tennessee River Basin are shown in Table 4-1 and Figure 4-1). Table 4-2. shows number of HRUs and mean, 10th percentile and 90th percentile of the SDRs estimated for the non-cultivated land HRUs in

the 8-digit watersheds in the Ohio-Tennessee River Basin (Figure 4-2). The mean, 10th and 90th percen-tile SDRs for the non-cropland HRUs are plotted in Figure 4-2.

In addition to SDR, an enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sediment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the outlet. The enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed outlet. The enrichment ratio is estimated for each APEX simula-tion site and SWAT HRUs and it varies from 0.5 to 1.5 (Average 1.0). As sediment is transported from the edge-of-field to the watershed outlet, coarse se-diments are deposited first while more of the fine se-diment that hold organic particles remain in suspen-sion, thus enriching the organic concentrations deli-vered to the watershed outlet.

A separate delivery ratio is used to simulate the transport of nitrate nitrogen, soluble phosphorus, and soluble pesticides. In general, the proportion of so-luble nutrients and pesticides delivered to rivers and streams is higher than the proportion attached to se-diments because they are not subject to sediment de-position.

4-3

Delivery Ratio used in CEAP in the Ohio-Tennessee River Basin

Figure 4-1 Map of the 8-digit watersheds in the Ohio-Tennessee River Basin

4-4

Table 4-1. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Ohio Riv-er Basin

HUC Cropland CRP Crop + CRP Points Mean

SDR

Points Mean

SDR

Points Mean

SDR

10th percentile

SDR

90th

percentile

SDR 5010001 1 0.37 1 0.37 0.37 0.37 5010002 3 0.43 1 0.38 4 0.42 0.36 0.50 5010003 3 0.37 3 0.37 0.36 0.38 5010004 10 0.35 1 0.32 11 0.34 0.32 0.41 5010005 2 0.38 2 0.38 0.31 0.45 5010006 15 0.35 15 0.35 0.32 0.38 5010007 5 0.37 1 0.36 6 0.37 0.34 0.40 5010008 2 0.43 2 0.43 0.40 0.46 5010009 2 0.42 2 0.42 0.41 0.42 5020001 1 0.46 1 0.46 0.46 0.46 5020005 2 0.32 2 0.32 0.31 0.32 5020006 10 0.37 1 0.32 11 0.36 0.32 0.48 5030101 5 0.40 2 0.36 7 0.39 0.35 0.52 5030102 15 0.34 15 0.34 0.31 0.38 5030103 23 0.35 23 0.35 0.32 0.39 5030105 6 0.38 6 0.38 0.36 0.41 5030106 1 0.36 1 0.36 0.36 0.36 5030201 2 0.41 2 0.41 0.38 0.44 5030202 1 0.35 1 0.35 0.35 0.35 5030204 10 0.36 10 0.36 0.33 0.38 5040001 30 0.34 2 0.31 32 0.34 0.30 0.37 5040002 16 0.39 7 0.38 23 0.39 0.35 0.43 5040003 21 0.36 2 0.35 23 0.36 0.33 0.39 5040004 11 0.48 2 0.43 13 0.47 0.42 0.54 5040006 7 0.41 7 0.41 0.35 0.50 5050001 1 0.32 1 0.32 0.32 0.32 5050002 1 0.43 1 0.43 0.43 0.43 5050003 1 0.47 1 0.47 0.47 0.47 5050008 1 0.33 1 0.33 0.33 0.33 5060001 76 0.36 14 0.36 90 0.36 0.33 0.40 5060002 22 0.38 5 0.36 27 0.38 0.35 0.39 5060003 26 0.44 8 0.38 34 0.42 0.36 0.54 5080001 78 0.38 10 0.35 88 0.38 0.33 0.45 5080002 43 0.37 2 0.34 45 0.37 0.34 0.41 5080003 54 0.37 14 0.34 68 0.36 0.32 0.43 5090101 3 0.36 3 0.36 0.35 0.37 5090103 1 0.34 1 0.34 0.34 0.34 5090201 44 0.36 10 0.34 54 0.35 0.32 0.41 5090202 65 0.40 7 0.35 72 0.39 0.35 0.45 5090203 24 0.44 1 0.40 25 0.44 0.39 0.51

5-1

5100101 8 0.33 8 0.33 0.31 0.39 5100102 4 0.37 4 0.37 0.35 0.39 5100204 2 0.41 2 0.41 0.39 0.42 5100205 17 0.37 17 0.37 0.33 0.47 5110001 25 0.32 15 0.30 40 0.31 0.29 0.34 5110002 21 0.35 5 0.32 26 0.35 0.31 0.40 5110003 11 0.41 6 0.36 17 0.39 0.34 0.50 5110004 13 0.35 9 0.32 22 0.33 0.30 0.37 5110005 26 0.37 2 0.32 28 0.36 0.32 0.40 5110006 26 0.40 14 0.36 40 0.38 0.34 0.42 5120101 30 0.41 11 0.38 41 0.40 0.35 0.47 5120102 5 0.45 7 0.42 12 0.43 0.41 0.49 5120103 20 0.42 2 0.39 22 0.42 0.37 0.49 5120104 16 0.37 8 0.38 24 0.37 0.33 0.44 5120105 12 0.43 2 0.39 14 0.42 0.37 0.51 5120106 39 0.37 10 0.31 49 0.36 0.31 0.42 5120107 16 0.43 16 0.43 0.39 0.49 5120108 67 0.38 8 0.35 75 0.38 0.34 0.44 5120109 38 0.39 2 0.34 40 0.38 0.36 0.43 5120110 11 0.38 1 0.35 12 0.38 0.34 0.44 5120111 60 0.38 9 0.33 69 0.37 0.33 0.43 5120112 87 0.37 9 0.33 96 0.37 0.33 0.42 5120113 70 0.37 5 0.35 75 0.37 0.33 0.43 5120114 68 0.37 32 0.35 100 0.37 0.31 0.42 5120115 38 0.40 47 0.35 85 0.38 0.33 0.44 5120201 61 0.36 2 0.32 63 0.36 0.32 0.41 5120202 44 0.41 4 0.34 48 0.40 0.34 0.49 5120203 29 0.39 4 0.33 33 0.38 0.33 0.43 5120204 30 0.42 1 0.37 31 0.42 0.36 0.46 5120205 9 0.45 9 0.45 0.37 0.52 5120206 26 0.43 1 0.35 27 0.43 0.37 0.52 5120207 33 0.40 33 0.40 0.36 0.45 5120208 26 0.35 22 0.33 48 0.34 0.31 0.38 5120209 18 0.40 4 0.40 22 0.40 0.34 0.47 5130101 1 0.42 1 0.42 0.42 0.42 5130103 10 0.33 10 0.33 0.31 0.41 5130104 1 0.35 1 0.35 0.35 0.35 5130107 8 0.44 1 0.42 9 0.44 0.42 0.48 5130108 1 0.42 1 0.40 2 0.41 0.40 0.42 5130201 3 0.37 3 0.37 0.35 0.38 5130203 2 0.42 1 0.37 3 0.40 0.37 0.42 5130204 2 0.43 2 0.32 4 0.38 0.32 0.47 5130205 19 0.33 22 0.31 41 0.32 0.30 0.35 5130206 43 0.38 3 0.36 46 0.37 0.34 0.45 5140101 20 0.38 20 0.38 0.35 0.44 5140102 14 0.35 1 0.32 15 0.35 0.32 0.37 5140103 11 0.36 1 0.31 12 0.35 0.31 0.42 5140104 26 0.35 15 0.33 41 0.34 0.32 0.38 5140201 26 0.38 1 0.34 27 0.37 0.33 0.44 5140202 50 0.40 50 0.40 0.35 0.46 5140203 21 0.39 25 0.35 46 0.37 0.33 0.40 5140204 28 0.42 33 0.38 61 0.40 0.34 0.49

5-2

5140205 17 0.39 11 0.34 28 0.37 0.33 0.46 5140206 36 0.43 27 0.39 63 0.41 0.36 0.51 6010101 2 0.42 2 0.42 0.37 0.46 6010102 1 0.44 1 0.44 0.44 0.44 6010103 1 0.42 1 0.42 0.42 0.42 6010105 2 0.35 2 0.35 0.34 0.35 6010108 1 0.33 1 0.33 0.33 0.33 6010201 1 0.45 1 0.45 0.45 0.45 6010204 3 0.40 3 0.40 0.38 0.43 6010207 1 0.40 1 0.40 0.40 0.40 6020004 1 0.39 1 0.39 0.39 0.39 6030001 11 0.40 11 0.40 0.35 0.45 6030002 23 0.35 3 0.33 26 0.35 0.32 0.41 6030003 9 0.37 2 0.35 11 0.37 0.35 0.44 6030004 6 0.41 1 0.40 7 0.41 0.37 0.50 6030005 16 0.37 8 0.33 24 0.36 0.32 0.45 6030006 1 0.38 1 0.38 0.38 0.38 6040001 14 0.36 17 0.33 31 0.35 0.30 0.36 6040002 5 0.35 3 0.34 8 0.34 0.33 0.37 6040003 2 0.43 4 0.32 6 0.36 0.31 0.43 6040004 1 0.36 1 0.36 0.36 0.36 6040005 13 0.36 22 0.34 35 0.35 0.31 0.38 6040006 23 0.43 21 0.39 44 0.41 0.36 0.46

5-3

Figure 4-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Ohio Riv-er Basin

Ohio River Basin

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

5010

001

5010

005

5010

009

5030

101

5030

106

5040

001

5040

006

5050

008

5080

001

5090

103

5100

101

5110

001

5110

005

5120

103

5120

107

5120

111

5120

115

5120

204

5120

208

5130

104

5130

203

5140

101

5140

201

5140

205

HUC8

S edi

m en

t D el

iver

y R

atio


5-4

Figure 4-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Tennessee River Basin

Tennessee River Basin

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

6010

101

6010

102

6010

103

6010

105

6010

108

6010

201

6010

204

6010

207

6020

004

6030

001

6030

002

6030

003

6030

004

6030

005

6030

006

6040

001

6040

002

6040

003

6040

004

6040

005

6040

006

HUC8

Sedi

men

t Del

iver

y R

atio


5-5

Table 4-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Ohio-Tennessee River Basin

HUC Subbasin Number of non-cropland HRUs simu-lated within

SWAT


SDR

90th Percen-tile

SDR

5010001 1 44 0.20 0.12 0.28 5010002 2 38 0.25 0.16 0.31 5010003 3 35 0.24 0.15 0.33 5010004 4 41 0.21 0.12 0.27 5010005 5 30 0.23 0.12 0.34 5010006 6 39 0.22 0.14 0.32 5010007 7 41 0.23 0.15 0.33 5010008 8 35 0.28 0.20 0.39 5010009 9 23 0.28 0.19 0.57 5020001 10 40 0.22 0.12 0.30 5020002 11 47 0.21 0.12 0.29 5020003 12 37 0.29 0.21 0.41 5020004 13 41 0.22 0.12 0.29 5020005 14 49 0.20 0.12 0.30 5020006 15 48 0.20 0.12 0.30 5030101 16 44 0.24 0.16 0.33 5030102 17 30 0.22 0.11 0.35 5030103 18 39 0.22 0.13 0.31 5030104 19 18 0.42 0.35 0.69 5030105 20 27 0.25 0.16 0.43 5030106 21 53 0.23 0.16 0.29 5030201 22 54 0.20 0.12 0.26 5030202 23 51 0.22 0.14 0.27 5030203 24 64 0.19 0.12 0.24 5030204 25 47 0.21 0.14 0.28 5040001 26 52 0.20 0.13 0.27 5040002 27 30 0.25 0.16 0.42 5040003 28 27 0.24 0.13 0.39 5040004 29 53 0.34 0.29 0.39 5040005 30 43 0.24 0.17 0.31 5040006 31 43 0.24 0.16 0.31 5050001 32 77 0.17 0.13 0.22 5050002 33 60 0.23 0.16 0.28 5050003 34 51 0.19 0.10 0.26 5050004 35 41 0.25 0.18 0.37 5050005 36 41 0.23 0.15 0.31 5050006 37 30 0.26 0.16 0.42 5050007 38 47 0.23 0.15 0.30 5050008 39 46 0.21 0.12 0.29 5050009 40 33 0.26 0.17 0.37 5060001 41 30 0.23 0.13 0.40 5060002 42 45 0.22 0.15 0.28

5-6

5060003 43 28 0.28 0.18 0.37 5070101 44 35 0.24 0.13 0.32 5070102 45 33 0.25 0.16 0.36 5070201 46 51 0.20 0.10 0.26 5070202 47 45 0.25 0.18 0.33 5070203 48 38 0.23 0.14 0.31 5070204 49 31 0.23 0.13 0.41 5080001 50 24 0.25 0.14 0.42 5080002 51 40 0.23 0.15 0.32 5080003 52 32 0.23 0.13 0.36 5090101 53 54 0.20 0.12 0.26 5090102 54 32 0.24 0.15 0.39 5090103 55 46 0.21 0.12 0.29 5090104 56 44 0.23 0.15 0.33 5090201 57 56 0.20 0.13 0.26 5090202 58 35 0.24 0.15 0.32 5090203 59 50 0.26 0.21 0.32 5100101 60 68 0.17 0.11 0.24 5100102 61 62 0.21 0.15 0.26 5100201 62 38 0.22 0.12 0.31 5100202 63 27 0.27 0.19 0.44 5100203 64 35 0.25 0.16 0.36 5100204 65 46 0.23 0.15 0.29 5100205 66 82 0.19 0.15 0.24 5110001 67 65 0.18 0.11 0.24 5110002 68 67 0.19 0.13 0.24 5110003 69 47 0.23 0.16 0.32 5110004 70 44 0.21 0.13 0.31 5110005 71 34 0.23 0.13 0.33 5110006 72 35 0.24 0.14 0.33 5120101 73 25 0.26 0.15 0.36 5120102 74 17 0.31 0.21 0.67 5120103 75 23 0.26 0.15 0.41 5120104 76 19 0.25 0.13 0.60 5120105 77 24 0.26 0.15 0.41 5120106 78 23 0.25 0.11 0.41 5120107 79 21 0.29 0.18 0.49 5120108 80 23 0.25 0.13 0.43 5120109 81 25 0.25 0.13 0.39 5120110 82 22 0.23 0.12 0.40 5120111 83 31 0.24 0.14 0.33 5120112 84 24 0.25 0.13 0.42 5120113 85 23 0.25 0.13 0.40 5120114 86 33 0.22 0.11 0.35 5120115 87 29 0.24 0.14 0.40 5120201 88 30 0.22 0.10 0.37 5120202 89 30 0.26 0.16 0.38 5120203 90 27 0.23 0.12 0.38 5120204 91 26 0.25 0.14 0.38 5120205 92 21 0.32 0.22 0.51 5120206 93 33 0.25 0.16 0.38 5120207 94 37 0.24 0.16 0.35

5-7

5120208 95 47 0.21 0.13 0.29 5120209 96 30 0.25 0.16 0.37 5130101 97 61 0.23 0.18 0.28 5130102 98 49 0.22 0.15 0.29 5130103 99 57 0.19 0.13 0.26 5130104 100 51 0.21 0.14 0.30 5130105 101 42 0.23 0.15 0.30 5130106 102 41 0.23 0.14 0.32 5130107 103 51 0.27 0.22 0.32 5130108 104 54 0.24 0.19 0.30 5130201 105 65 0.20 0.15 0.26 5130202 106 37 0.23 0.15 0.34 5130203 107 64 0.22 0.17 0.28 5130204 108 54 0.20 0.13 0.28 5130205 109 49 0.19 0.11 0.28 5130206 110 50 0.22 0.14 0.27 5140101 111 47 0.22 0.14 0.30 5140102 112 63 0.21 0.15 0.26 5140103 113 54 0.20 0.12 0.27 5140104 114 59 0.20 0.14 0.25 5140201 115 41 0.22 0.13 0.30 5140202 116 27 0.26 0.15 0.40 5140203 117 44 0.23 0.15 0.30 5140204 118 34 0.25 0.16 0.35 5140205 119 34 0.23 0.13 0.34 5140206 120 47 0.25 0.19 0.31 6010101 121 42 0.21 0.12 0.32 6010102 122 59 0.24 0.20 0.29 6010103 123 48 0.25 0.20 0.33 6010104 124 53 0.19 0.13 0.27 6010105 125 63 0.20 0.14 0.23 6010106 126 40 0.23 0.15 0.34 6010107 127 53 0.28 0.25 0.32 6010108 128 56 0.20 0.13 0.27 6010201 129 57 0.26 0.21 0.31 6010202 130 36 0.27 0.19 0.35 6010203 131 35 0.27 0.19 0.37 6010204 132 49 0.26 0.21 0.31 6010205 133 56 0.18 0.09 0.25 6010206 134 45 0.23 0.14 0.30 6010207 135 48 0.26 0.19 0.33 6010208 136 50 0.23 0.17 0.32 6020001 137 55 0.21 0.16 0.28 6020002 138 57 0.21 0.16 0.27 6020003 139 38 0.24 0.15 0.36 6020004 140 43 0.20 0.11 0.30 6030001 141 58 0.21 0.16 0.29 6030002 142 63 0.19 0.15 0.27 6030003 143 68 0.20 0.15 0.26 6030004 144 75 0.22 0.17 0.26 6030005 145 65 0.21 0.17 0.27 6030006 146 47 0.23 0.17 0.31

5-8

6040001 147 62 0.20 0.15 0.28 6040002 148 63 0.20 0.16 0.26 6040003 149 56 0.21 0.15 0.27 6040004 150 44 0.27 0.21 0.33 6040005 151 46 0.22 0.14 0.31 6040006 152 38 0.28 0.21 0.36

5-9

5-10

Figure 4-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Ohio River Basin

Figure 4-3. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Tennessee River Basin

Ohio River Basin

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Tennessee River Basin

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Chapter 5

Delivery Ratio used in CEAP Cropland Modeling in the Great Lakes Basin

5-11

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nu-trients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009 ) in the Great Lakes Basin. APEX simulates all of the basic biological, chemical, hydrological, and meteo-rological processes of farming systems and their interac-tions. Soil erosion is simulated over time, including wind erosion, sheet and rill erosion. The nitrogen, phosphorus, and carbon cycles are simulated, including chemical trans-formations in the soil that affect their availability for plant growth or for transport from the field.

While the APEX model was used to simulate the culti-vated cropland, the SWAT model was used to simulate the non-cultivated cropland in the 8-digit watersheds of the river basin. SWAT is a physical process model with a dai-ly time step (Arnold and Fohrer 2005; Arnold et al. 1998; Gassman et al. 2007). The hydrologic cycle in the model is divided into two parts. The land phase of the hydrologic cycle, or upland processes, simulates the amount of water, sediment, nutrients, and pesticides delivered from the land to the outlet of each watershed. The routing phase of the hydrologic cycle, or channel processes, simulates the movement of water, sediment, nutrients, and pesticides from the outlet of the upstream watershed through the main channel network to the watershed outlet.

In SWAT, each 8-digit watershed is divided into multiple Hydrologic Response Units (HRUs) that have homogene-ous land use, soil, and slope. SWAT is used to simulate the fate and transport of water, sediment, nutrients, and pesti-cides from various non-cropland HRUs as described in Chapter 1.

Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the deposition is temporary. Eroded soil may deposit in lower spots, flatter lands, depo-sited at the edge of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary stream channels during transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National As-sessment modeling. The SDR used in this study is a func-tion of the ratio of the time of concentration for the HRU (land uses other than cultivated cropland) or field (culti-vated cropland) to the time of concentration for the wa-tershed (8-digit HUC). The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to

Delivery Ratio used in CEAP in the Great Lakes Basin

the time the surface water runoff reaches the outlet of the watershed. It is calculated by summing the overland flow time (the time it takes for flow from the remotest point in the watershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream channels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concentration for the HRU is derived from characteristics of the watershed, the HRU, and the proportion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique delivery ratio within each watershed, as does each HRU. The description of the sediment delivery ratio procedure is provided in Chapter 1.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE de-veloped from Theory) (Williams 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to de-termine the amount of sediment that reach the 8-digit wa-tershed outlet from each APEX simulation site. The sedi-ment load from apex simulation sites are aggregated for the 8-digit watershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality ef-fects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimating the SDR for each HRU, the SDR is applied to determine the amount of sediment that reach the 8-digit watershed outlet.

Sediment delivery ratios were estimated to account for sediment losses or deposition occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated cropland and CRP and non-cropland HRUs in the Great Lakes Basin (Figure 5-1). The Great Lakes Basin has a drainage area of 111.58 mil-lion acres. The cultivated cropland and land enrolled in the CRP General Signup is about 16 percent of the Great Lakes Basin. A total of 111, 8-digit watersheds are in the Great Lakes Basin including the five lakes (Figure 5-1). Within each 8-digit watershed, the percent of cultivated cropland and CRP area and non-cultivated cropland area varies widely across the entire basin.

A total of 1843 representative cultivated fields (1418 NRI-CEAP cropland points and 425 CRP points) were setup to run using APEX. Thirty-six out of 111, 8-digit watersheds in the Great Lakes have no CEAP points; the thirty-six 8-digit watersheds have zero or fewer than 7% percentage cultivated.

Non-cultivated land is distributed over 84 percent of the Great Lakes Basin. Within each 8-digit watershed, non-

5-12


cultivated land uses such as pasture, range, hay, horticul-ture, forest deciduous, forest mixed, forest evergreen, ur-ban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 3900 HRUs are simulated in SWAT for the Great Lakes Basin.

Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each culti-vated cropland site simulated in an 8-digit watershed and so as for HRU. The number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit water-sheds in the Great Lakes Basin are shown in Table 5-1 and Figure 5-1). Table 5-2. shows number of HRUs and mean, 10th percentile and 90th percentile of the SDRs estimated for the non-cultivated land HRUs in the 8-digit watersheds in the Great Lakes Basin (Figure 5-1). The mean, 10th and 90th percentile SDRs for the non-cropland HRUs are plot-ted in Figure 5-2.

In addition to SDR, an enrichment ratio was used to simu-late organic nitrogen, organic phosphorus, and sediment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the outlet. The enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed out-let. The enrichment ratio is estimated for each APEX si-mulation site and SWAT HRUs and it varies from 0.5 to 1.5 (Average 1.0). As sediment is transported from the edge-of-field to the watershed outlet, coarse sediments are deposited first while more of the fine sediment that hold organic particles remain in suspension, thus enriching the organic concentrations delivered to the watershed outlet.

A separate delivery ratio is used to simulate the transport of nitrate nitrogen, soluble phosphorus, and soluble pesti-cides. In general, the proportion of soluble nutrients and pesticides delivered to rivers and streams is higher than the proportion attached to sediments because they are not sub-ject to sediment deposition.

5-13


Figure 5-1 Map of the 8-digit watersheds in the Great Lakes Basin

5-14


Table 5-1. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Great Lakes Basin

HUC Cropland CRP Crop + CRP Points Mean

SDR

Points Mean

SDR

Point s

Mean

SDR

10th

percentile SDR

90th

percentile SDR

4020102 1 0.41 1 0.41 0.41 0.41 4020103 2 0.49 2 0.49 0.48 0.49 4030101 54 0.41 12 0.39 66 0.41 0.37 0.46 4030102 26 0.55 17 0.54 43 0.54 0.51 0.58 4030103 8 0.44 3 0.43 11 0.44 0.40 0.48 4030104 5 0.40 8 0.39 13 0.40 0.37 0.44 4030105 5 0.35 5 0.35 0.33 0.38 4030108 2 0.31 2 0.31 0.30 0.32 4030109 1 0.38 1 0.38 0.38 0.38 4030112 1 0.45 1 0.45 0.45 0.45 4030201 25 0.34 15 0.33 40 0.34 0.31 0.36 4030202 29 0.36 25 0.34 54 0.35 0.32 0.39 4030203 8 0.41 6 0.43 14 0.42 0.39 0.48 4030204 6 0.40 3 0.39 9 0.40 0.34 0.47 4040001 21 0.44 3 0.39 24 0.43 0.38 0.52 4040002 12 0.44 3 0.41 15 0.43 0.40 0.52 4040003 23 0.39 5 0.37 28 0.38 0.35 0.46 4050001 200 0.34 48 0.32 248 0.34 0.30 0.40 4050002 11 0.46 11 0.46 0.42 0.58 4050003 57 0.33 4 0.32 61 0.33 0.30 0.38 4050004 31 0.36 1 0.31 32 0.35 0.32 0.40 4050005 13 0.46 3 0.45 16 0.46 0.37 0.51 4050006 17 0.38 5 0.35 22 0.37 0.33 0.45 4050007 9 0.36 4 0.34 13 0.35 0.32 0.39 4060101 12 0.39 12 0.39 0.36 0.45 4060102 6 0.32 2 0.30 8 0.31 0.30 0.34 4060103 1 0.33 1 0.33 0.33 0.33 4060104 4 0.42 4 0.42 0.39 0.45 4060105 1 0.35 1 0.36 2 0.35 0.35 0.36 4070006 2 0.39 2 0.39 0.39 0.39 4080101 2 0.49 1 0.46 3 0.48 0.43 0.54 4080102 10 0.48 1 0.44 11 0.48 0.43 0.55 4080103 25 0.51 5 0.48 30 0.51 0.45 0.57 4080104 14 0.51 5 0.53 19 0.51 0.46 0.59 4080201 5 0.41 1 0.39 6 0.41 0.35 0.49 4080202 14 0.43 4 0.37 18 0.41 0.35 0.48 4080203 17 0.45 3 0.49 20 0.46 0.41 0.53 4080204 16 0.37 2 0.37 18 0.37 0.34 0.43 4080205 13 0.41 4 0.38 17 0.40 0.35 0.48 4080206 7 0.50 7 0.50 0.44 0.59 4090001 27 0.40 3 0.45 30 0.41 0.36 0.47

5-15


4090003 6 0.44 6 0.44 0.39 0.55 4090005 19 0.37 19 0.37 0.33 0.47 4100001 29 0.52 29 0.52 0.45 0.60 4100002 62 0.40 21 0.35 83 0.39 0.33 0.48 4100003 80 0.42 95 0.40 175 0.41 0.36 0.49 4100004 30 0.48 2 0.43 32 0.47 0.41 0.57 4100005 15 0.51 8 0.49 23 0.50 0.43 0.58 4100006 41 0.42 35 0.39 76 0.41 0.37 0.48 4100007 66 0.47 12 0.42 78 0.46 0.41 0.54 4100008 29 0.41 2 0.36 31 0.40 0.37 0.45 4100009 31 0.44 1 0.39 32 0.44 0.38 0.49 4100010 22 0.45 2 0.47 24 0.45 0.40 0.47 4100011 48 0.41 12 0.43 60 0.41 0.35 0.47 4100012 39 0.48 15 0.47 54 0.48 0.42 0.54 4110001 26 0.44 5 0.42 31 0.44 0.39 0.49 4110002 3 0.35 3 0.35 0.31 0.37 4110003 1 0.45 1 0.45 0.45 0.45 4110004 3 0.41 1 0.44 4 0.42 0.38 0.44 4120101 2 0.47 2 0.47 0.46 0.48 4120102 3 0.40 1 0.42 4 0.40 0.39 0.42 4120103 1 0.45 1 0.43 2 0.44 0.43 0.45 4120104 9 0.44 2 0.42 11 0.44 0.36 0.52 4130001 14 0.45 4 0.43 18 0.44 0.39 0.49 4130002 6 0.37 1 0.36 7 0.37 0.35 0.40 4130003 18 0.44 1 0.41 19 0.44 0.40 0.55 4140101 9 0.49 2 0.46 11 0.48 0.43 0.59 4140102 4 0.53 4 0.53 0.49 0.59 4140201 49 0.36 2 0.34 51 0.36 0.32 0.38 4140202 4 0.34 1 0.32 5 0.34 0.32 0.36 4140203 1 0.44 1 0.44 0.44 0.44 4150101 4 0.41 4 0.41 0.35 0.48 4150102 1 0.46 1 0.46 0.46 0.46 4150302 1 0.52 1 0.52 0.52 0.52 4150303 1 0.48 1 0.48 0.48 0.48

5-16


Figure 5-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Great Lakes Basin

Great Lakes

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5-17


Table 5-2. Mean and percentiles of sediment delivery ratio (ratio of sediment delivered at 8-digit watershed outlet by se-diment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Great Lakes Basin

HUC Subbasin Number of non-cropland HRUs simulated within

SWAT


SDR

90th Percen-tile

SDR

4010101 1 49 0.34 0.28 0.39 4010102 2 37 0.49 0.44 0.52 4010201 3 41 0.24 0.18 0.29 4010202 4 30 0.25 0.16 0.32 4010301 5 46 0.34 0.29 0.39 4010302 6 47 0.28 0.22 0.34 4020101 7 39 0.33 0.25 0.38 4020102 8 48 0.27 0.20 0.31 4020103 9 32 0.39 0.33 0.49 4020104 10 39 0.26 0.17 0.33 4020105 11 42 0.31 0.25 0.36 4020201 12 44 0.41 0.34 0.45 4020202 13 36 0.26 0.18 0.35 4020203 14 32 0.38 0.33 0.44 4020300 15 4 0.51 0.26 0.79 4030101 16 37 0.29 0.22 0.38 4030102 17 41 0.48 0.44 0.52 4030103 18 33 0.33 0.27 0.43 4030104 19 38 0.30 0.23 0.36 4030105 20 41 0.24 0.16 0.33 4030106 21 46 0.25 0.17 0.32 4030107 22 44 0.27 0.21 0.33 4030108 23 43 0.23 0.15 0.30 4030109 24 37 0.30 0.24 0.37 4030110 25 47 0.24 0.18 0.32 4030111 26 39 0.33 0.27 0.38 4030112 27 32 0.34 0.27 0.45 4030201 28 26 0.25 0.12 0.35 4030202 29 26 0.25 0.13 0.35 4030203 30 29 0.28 0.20 0.43 4030204 31 27 0.27 0.16 0.41 4040001 32 37 0.32 0.25 0.39 4040002 33 26 0.32 0.25 0.51 4040003 34 34 0.27 0.19 0.33 4050001 35 26 0.25 0.14 0.45 4050002 36 36 0.34 0.28 0.42 4050003 37 38 0.23 0.15 0.32 4050004 38 44 0.22 0.15 0.29 4050005 39 35 0.28 0.21 0.37 4050006 40 36 0.25 0.16 0.32 4050007 41 41 0.23 0.16 0.31 4060101 42 31 0.28 0.19 0.37

5-18


4060102 43 31 0.23 0.11 0.35 4060103 44 48 0.21 0.13 0.27 4060104 45 37 0.27 0.20 0.34 4060105 46 38 0.26 0.18 0.33 4060106 47 48 0.29 0.23 0.33 4060107 48 38 0.51 0.46 0.55 4060200 49 5 0.54 0.45 0.63 4070001 50 36 0.40 0.35 0.45 4070002 51 34 0.34 0.29 0.41 4070003 52 39 0.34 0.29 0.40 4070004 53 38 0.28 0.22 0.35 4070005 54 46 0.28 0.22 0.34 4070006 55 45 0.26 0.21 0.31 4070007 56 42 0.25 0.18 0.33 4080101 57 43 0.29 0.21 0.33 4080102 58 32 0.37 0.29 0.43 4080103 59 30 0.34 0.27 0.43 4080104 60 35 0.36 0.31 0.43 4080201 61 40 0.29 0.21 0.33 4080202 62 40 0.28 0.20 0.33 4080203 63 38 0.35 0.30 0.41 4080204 64 43 0.24 0.16 0.32 4080205 65 42 0.26 0.20 0.32 4080206 66 19 0.38 0.32 0.45 4080300 67 2 0.75 0.67 0.83 4090001 68 38 0.27 0.19 0.34 4090002 69 26 0.54 0.49 0.61 4090003 70 36 0.31 0.25 0.38 4090004 71 26 0.36 0.28 0.52 4090005 72 35 0.26 0.18 0.39 4100001 73 36 0.37 0.31 0.42 4100002 74 32 0.25 0.17 0.37 4100003 75 30 0.31 0.24 0.41 4100004 76 22 0.37 0.30 0.54 4100005 77 21 0.37 0.31 0.50 4100006 78 24 0.29 0.20 0.47 4100007 79 25 0.34 0.26 0.46 4100008 80 20 0.30 0.20 0.50 4100009 81 23 0.30 0.20 0.48 4100010 82 23 0.30 0.19 0.47 4100011 83 25 0.27 0.18 0.39 4100012 84 25 0.32 0.24 0.45 4110001 85 38 0.29 0.22 0.37 4110002 86 33 0.24 0.16 0.32 4110003 87 28 0.36 0.29 0.47 4110004 88 33 0.27 0.19 0.40 4120101 89 45 0.31 0.26 0.36 4120102 90 42 0.26 0.20 0.35 4120103 91 45 0.31 0.26 0.39 4120104 92 52 0.28 0.23 0.33 4120200 93 1 0.95 0.95 0.95

5-19


4130001 94 43 0.34 0.28 0.40 4130002 95 49 0.23 0.17 0.29 4130003 96 39 0.31 0.26 0.39 4140101 97 44 0.37 0.32 0.42 4140102 98 46 0.41 0.38 0.45 4140201 99 36 0.23 0.14 0.33 4140202 100 42 0.24 0.17 0.32 4140203 101 39 0.31 0.25 0.37 4150101 102 42 0.25 0.18 0.31 4150102 103 55 0.41 0.36 0.44 4150200 104 2 0.60 0.26 0.95 4150301 105 17 0.55 0.49 0.69 4150302 106 36 0.38 0.34 0.41 4150303 107 44 0.31 0.26 0.36 4150304 108 31 0.32 0.26 0.41 4150305 109 41 0.24 0.19 0.29 4150306 110 45 0.31 0.26 0.39 4150307 111 40 0.32 0.26 0.39

Figure 5-3. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Great Lakes Basin

Great Lakes

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HUC8

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t Del

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atio


5-20

Chapter 6

Delivery Ratio used in CEAP Cropland Modeling in the Missouri River Basin

6‐1

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nutrients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009 ) in the Missouri River Basin. APEX simulates all of the basic biological, chemical, hydrological, and meteorological processes of farming systems and their interactions. Soil erosion is simulated over time, including wind erosion, sheet and rill erosion. The nitrogen, phosphorus, and carbon cycles are simulated, including chemical transformations in the soil that affect their availability for plant growth or for transport from the field.

While the APEX model was used for simulate the cultivated cropland and the SWAT model was used to simulate the non-cultivated cropland in the 8-digit watersheds of the river basin. SWAT is a physical process model with a daily time step (Arnold and Fohrer 2005; Arnold et al. 1998; Gassman et al. 2007). The hydrologic cycle in the model is divided into two parts. The land phase of the hydrologic cycle, or upland processes, simulates the amount of water, sediment, nutrients, and pesticides delivered from the land to the outlet of each watershed. The routing phase of the hydrologic cycle, or channel processes, simulates the movement of water, sediment, nutrients, and pesticides from the outlet of the upstream watershed through the main channel network to the watershed outlet.

In SWAT, each 8-digit watershed is divided into multiple Hydrologic Response Units (HRUs) that have homogeneous land use, soil, and slope. SWAT is used to simulate the fate and transport of water, sediment, nutrients, and pesticides from various non-cropland HRUs as described in Chapter 1.

Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the deposition is temporary. Eroded soil may deposit in lower spots, flatter lands, deposited at the edge of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary stream channels during transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National Assessment modeling. The SDR used in this study is a function of the ratio of the time of concentration for the HRU (land uses other than cultivated cropland) or

Delivery Ratio used in CEAP in the Missouri River Basin

field (cultivated cropland) to the time of concentration for the watershed (8-digit HUC). The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to the time the surface water runoff reaches the outlet of the watershed. It is calculated by summing the overland flow time (the time it takes for flow from the remotest point in the watershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream channels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concentration for the HRU is derived from characteristics of the watershed, the HRU, and the proportion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique delivery ratio within each watershed, as does each HRU. The description of the sediment delivery ratio procedure is provided in Chapter 1.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE developed from Theory) (Williams 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to determine the amount of sediment that reach the 8-digit watershed outlet from each APEX simulation site. The sediment load from apex simulation sites are aggregated for the 8-digit watershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality effects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimating the SDR for each HRU, the SDR is applied to determine the amount of sediment that reaches the 8-digit watershed outlet.

Sediment delivery ratios were estimated to account for sediment losses or deposition occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated cropland and CRP and non-cropland HRUs in the Missouri River Basin (Figure 6-1). The Missouri River Basin has a drainage area of 327 million acres. The cultivated cropland and land enrolled in the CRP General Signup is about 29 percent of the Missouri River Basin. A total of 310, 8-digit watersheds are in the Missouri River Basin (Figure 6-1). Within each 8-digit watershed, the percent of cultivated cropland and CRP area and non-cultivated cropland area varies widely across the entire basin.

6‐2

A total of 8186 representative cultivated fields (3916 NRI-CEAP cropland points and 4270 CRP points) were setup to run using APEX. Fifty-four out of 310, 8-digit watersheds in the Missouri have no CEAP points; the fifty-four 8-digit watersheds have zero or fewer than 7% percentage cultivated.

Non-cultivated land is distributed over 71 percent of the Missouri River Basin. Within each 8-digit watershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 11,716 HRUs are simulated in SWAT for the Missouri River Basin.

Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each cultivated cropland site simulated in an 8-digit watershed and so as for HRU. The number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit watersheds in the Missouri River Basin are shown in Table 6-1 and Figure 6-2. Table 6-2 shows number of HRUs and mean, 10th percentile and 90th percentile of the SDRs estimated for the non-cultivated land HRUs in the 8-digit watersheds in the Missouri River Basin (Figure 6-1). The mean, 10th and 90th percentile SDRs for the non-cropland HRUs are plotted in Figure 6-3.


In addition to SDR, an enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sediment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the outlet. The enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed outlet. The enrichment ratio is estimated for each APEX simulation site and SWAT HRUs and it varies from 0.5 to 1.5 (Average 1.0). As sediment is transported from the edge-of-field to the watershed outlet, coarse sediments are deposited first while more of the fine sediment that hold organic particles remain in suspension, thus enriching the organic concentrations delivered to the watershed outlet.

A separate delivery ratio is used to simulate the transport of nitrate nitrogen, soluble phosphorus, and soluble pesticides. In general, the proportion of soluble nutrients and pesticides delivered to rivers and streams is higher than the proportion attached to sediments because they are not subject to sediment deposition.

6‐3


Figure 6-1. Map of the 8-digit watersheds in the Missouri River Basin .

6‐4


Table 6-1. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Missouri River Basin.

HUC Cropland CRP Crop + CRP Poi nts

Mea n

SDR

Points Mean SDR

Points Mean SDR

10th

percen tile

90th

percentile

10020003 1 0.44 1 0.44 0.44 0.44 10020005 1 0.48 10 0.36 11 0.37 0.34 0.46 10020006 1 0.43 1 0.43 0.43 0.43 10020008 5 0.41 1 0.43 6 0.41 0.38 0.43 10030101 11 0.36 9 0.38 20 0.37 0.34 0.40 10030102 13 0.48 9 0.47 22 0.48 0.45 0.52 10030103 2 0.39 2 0.39 0.39 0.40 10030104 6 0.43 9 0.39 15 0.40 0.35 0.48 10030105 1 0.43 1 0.43 0.43 0.43 10030201 1 0.45 2 0.35 3 0.39 0.35 0.45 10030202 8 0.44 4 0.37 12 0.42 0.36 0.52 10030203 23 0.35 41 0.35 64 0.35 0.32 0.38 10030204 7 0.42 23 0.36 30 0.38 0.34 0.43 10030205 14 0.39 16 0.40 30 0.39 0.37 0.44 10040101 2 0.48 8 0.46 10 0.46 0.41 0.53 10040102 13 0.42 13 0.42 0.39 0.45 10040103 22 0.39 10 0.38 32 0.39 0.36 0.40 10040104 3 0.37 2 0.35 5 0.36 0.35 0.39 10040105 4 0.40 7 0.37 11 0.38 0.36 0.41 10040106 4 0.37 14 0.37 18 0.37 0.36 0.39 10040201 6 0.37 16 0.37 22 0.37 0.34 0.39 10040202 8 0.35 8 0.35 0.33 0.38 10040203 1 0.46 5 0.41 6 0.42 0.39 0.46 10040204 3 0.39 1 0.35 4 0.38 0.35 0.40 10040205 3 0.40 1 0.44 4 0.41 0.38 0.44 10050001 1 0.48 1 0.48 0.48 0.48 10050002 5 0.40 15 0.42 20 0.42 0.38 0.46 10050004 7 0.42 13 0.41 20 0.41 0.37 0.45 10050005 5 0.43 7 0.43 12 0.43 0.40 0.46 10050006 8 0.46 20 0.47 28 0.47 0.44 0.49 10050008 1 0.44 2 0.46 3 0.46 0.44 0.46 10050009 1 0.46 3 0.48 4 0.47 0.45 0.51

6‐5


10050010 8 0.38 7 0.36 15 0.37 0.32 0.40 10050011 1 0.38 2 0.39 3 0.39 0.36 0.42 10050012 12 0.41 11 0.37 23 0.40 0.35 0.47 10050013 5 0.38 5 0.38 0.38 0.39 10050014 11 0.37 11 0.37 0.35 0.39 10050015 4 0.39 4 0.39 0.37 0.40 10050016 2 0.41 5 0.39 7 0.40 0.37 0.45 10060001 21 0.39 22 0.37 43 0.38 0.34 0.47 10060002 13 0.35 34 0.35 47 0.35 0.33 0.37 10060003 20 0.39 23 0.39 43 0.39 0.36 0.43 10060004 10 0.39 10 0.39 20 0.39 0.37 0.42 10060005 15 0.42 4 0.41 19 0.42 0.39 0.48 10060006 27 0.33 67 0.33 94 0.33 0.31 0.36 10060007 8 0.43 38 0.41 46 0.41 0.38 0.44 10070003 3 0.46 4 0.34 7 0.39 0.33 0.49 10070004 10 0.41 9 0.41 19 0.41 0.37 0.45 10070006 3 0.40 2 0.35 5 0.38 0.34 0.43 10070007 12 0.40 10 0.36 22 0.38 0.35 0.41 10070008 2 0.44 2 0.44 0.43 0.44 10080007 13 0.42 13 0.42 0.39 0.43 10080008 1 0.43 1 0.43 0.43 0.43 10080009 4 0.46 4 0.46 0.44 0.47 10080011 1 0.59 1 0.59 0.59 0.59 10080014 6 0.45 6 0.45 0.43 0.46 10080015 5 0.41 4 0.39 9 0.40 0.37 0.43 10080016 1 0.39 3 0.37 4 0.37 0.35 0.39 10090202 4 0.34 4 0.20 8 0.27 0.19 0.36 10090208 1 0.38 1 0.38 0.38 0.38 10090209 3 0.34 3 0.34 0.32 0.37 10090210 1 0.39 7 0.37 8 0.38 0.35 0.41 10100001 5 0.36 5 0.34 10 0.35 0.32 0.41 10100002 1 0.47 1 0.47 0.47 0.47 10100004 33 0.33 23 0.31 56 0.32 0.30 0.35 10100005 4 0.36 12 0.37 16 0.37 0.35 0.41 10110101 47 0.35 70 0.34 117 0.34 0.31 0.38 10110102 12 0.35 19 0.35 31 0.35 0.32 0.39 10110201 3 0.36 11 0.34 14 0.34 0.32 0.36 10110202 1 0.36 1 0.36 0.36 0.36 10110203 9 0.33 19 0.32 28 0.32 0.31 0.35 10110204 18 0.37 16 0.35 34 0.36 0.34 0.38 10110205 3 0.34 7 0.32 10 0.32 0.30 0.35 10120106 1 0.43 1 0.43 0.43 0.43

6‐6


10120107 1 0.43 1 0.43 0.43 0.43 10120108 2 0.42 2 0.42 0.41 0.44 10120109 1 0.45 1 0.45 0.45 0.45 10120110 1 0.41 1 0.41 0.41 0.41 10120111 1 0.41 1 0.39 2 0.40 0.39 0.41 10120112 1 0.49 1 0.49 0.49 0.49 10120113 1 0.37 3 0.33 4 0.34 0.32 0.37 10120201 1 0.33 2 0.19 3 0.24 0.18 0.33 10120202 3 0.34 1 0.35 4 0.34 0.33 0.35 10130101 21 0.34 23 0.35 44 0.35 0.32 0.38 10130102 17 0.35 36 0.34 53 0.34 0.32 0.37 10130103 14 0.33 92 0.32 106 0.32 0.30 0.35 10130104 9 0.44 28 0.44 37 0.44 0.41 0.48 10130105 23 0.35 20 0.34 43 0.34 0.31 0.36 10130106 22 0.37 51 0.36 73 0.36 0.34 0.39 10130201 21 0.33 23 0.33 44 0.33 0.31 0.36 10130202 11 0.34 55 0.33 66 0.33 0.32 0.35 10130203 6 0.35 13 0.33 19 0.34 0.32 0.37 10130204 17 0.33 32 0.32 49 0.32 0.30 0.35 10130205 11 0.33 52 0.32 63 0.32 0.30 0.34 10130206 6 0.36 6 0.36 0.35 0.38 10130301 9 0.36 22 0.36 31 0.36 0.34 0.39 10130302 2 0.35 3 0.34 5 0.34 0.34 0.35 10130303 4 0.34 4 0.34 8 0.34 0.32 0.36 10130306 4 0.31 6 0.33 10 0.32 0.31 0.34 10140101 56 0.33 18 0.32 74 0.33 0.30 0.35 10140102 8 0.34 17 0.33 25 0.33 0.31 0.34 10140103 9 0.38 15 0.38 24 0.38 0.34 0.41 10140104 4 0.43 13 0.39 17 0.40 0.38 0.45 10140105 11 0.40 6 0.40 17 0.40 0.37 0.43 10140201 3 0.34 5 0.33 8 0.34 0.32 0.36 10140202 1 0.32 1 0.32 0.32 0.32 10140203 4 0.34 4 0.32 8 0.33 0.31 0.37 10140204 14 0.37 11 0.37 25 0.37 0.35 0.42 10150001 9 0.36 3 0.33 12 0.35 0.32 0.38 10150002 3 0.36 3 0.36 0.35 0.38 10150003 14 0.33 22 0.32 36 0.33 0.30 0.35 10150004 5 0.34 5 0.34 10 0.34 0.30 0.40 10150006 3 0.34 3 0.35 6 0.35 0.33 0.37 10150007 15 0.39 6 0.36 21 0.38 0.33 0.42 10160001 28 0.36 52 0.37 80 0.37 0.34 0.38 10160002 6 0.36 28 0.35 34 0.35 0.32 0.38

6‐7


10160003 48 0.37 88 0.37 136 0.37 0.33 0.40 10160004 13 0.39 43 0.39 56 0.39 0.37 0.41 10160005 9 0.43 5 0.44 14 0.43 0.39 0.48 10160006 44 0.39 43 0.38 87 0.38 0.34 0.42 10160007 9 0.48 10 0.48 19 0.48 0.44 0.59 10160008 16 0.37 13 0.36 29 0.37 0.35 0.38 10160009 14 0.37 4 0.39 18 0.37 0.33 0.41 10160010 8 0.40 42 0.39 50 0.39 0.37 0.43 10160011 72 0.38 32 0.37 104 0.38 0.35 0.41 10170101 83 0.36 79 0.33 162 0.34 0.31 0.38 10170102 87 0.34 15 0.33 102 0.34 0.31 0.37 10170103 9 0.42 2 0.42 11 0.42 0.39 0.46 10170201 19 0.37 24 0.35 43 0.36 0.33 0.38 10170202 34 0.40 35 0.39 69 0.40 0.37 0.44 10170203 100 0.33 21 0.33 121 0.33 0.30 0.35 10170204 82 0.37 5 0.33 87 0.37 0.34 0.43 10180008 3 0.22 3 0.22 0.21 0.23 10180009 25 0.40 50 0.29 75 0.33 0.22 0.42 10180011 1 0.41 6 0.24 7 0.27 0.23 0.41 10180012 5 0.38 30 0.27 35 0.28 0.23 0.39 10180013 9 0.41 31 0.40 40 0.41 0.38 0.46 10180014 4 0.39 1 0.33 5 0.38 0.33 0.41 10190003 24 0.38 6 0.39 30 0.38 0.35 0.42 10190005 1 0.48 1 0.48 0.48 0.48 10190007 4 0.44 3 0.39 7 0.42 0.39 0.44 10190008 5 0.48 5 0.48 0.44 0.51 10190009 3 0.41 5 0.40 8 0.40 0.37 0.43 10190010 6 0.42 4 0.43 10 0.42 0.41 0.43 10190011 16 0.38 25 0.37 41 0.37 0.35 0.40 10190012 34 0.39 25 0.37 59 0.38 0.35 0.44 10190013 10 0.40 20 0.39 30 0.40 0.36 0.42 10190014 3 0.43 1 0.41 4 0.42 0.41 0.45 10190015 14 0.40 35 0.26 49 0.30 0.23 0.42 10190016 17 0.40 44 0.32 61 0.34 0.24 0.42 10190017 5 0.44 55 0.41 60 0.42 0.30 0.47 10190018 17 0.39 3 0.38 20 0.39 0.35 0.44 10200101 27 0.38 2 0.31 29 0.37 0.32 0.41 10200102 6 0.43 6 0.43 0.36 0.44 10200103 35 0.41 4 0.34 39 0.40 0.34 0.44 10200201 15 0.38 9 0.32 24 0.36 0.31 0.44 10200202 19 0.44 4 0.42 23 0.43 0.39 0.50 10200203 41 0.37 18 0.35 59 0.37 0.34 0.40

6‐8


10210002 1 0.34 1 0.34 0.34 0.34 10210003 14 0.34 4 0.32 18 0.34 0.30 0.41 10210004 5 0.33 2 0.32 7 0.33 0.28 0.37 10210005 2 0.37 1 0.33 3 0.36 0.33 0.37 10210006 2 0.30 2 0.30 0.28 0.32 10210007 12 0.39 3 0.33 15 0.38 0.32 0.44 10210008 3 0.37 3 0.37 0.36 0.39 10210009 19 0.34 18 0.32 37 0.33 0.30 0.40 10210010 11 0.35 12 0.32 23 0.33 0.29 0.39 10220001 12 0.32 18 0.31 30 0.31 0.29 0.34 10220002 13 0.40 4 0.36 17 0.39 0.35 0.47 10220003 46 0.35 10 0.32 56 0.34 0.31 0.37 10220004 32 0.34 11 0.32 43 0.33 0.30 0.36 10230001 62 0.35 41 0.30 103 0.33 0.29 0.39 10230002 31 0.39 1 0.37 32 0.39 0.32 0.47 10230003 52 0.35 14 0.31 66 0.34 0.29 0.43 10230004 15 0.40 8 0.34 23 0.38 0.32 0.47 10230005 11 0.34 5 0.32 16 0.33 0.31 0.36 10230006 33 0.37 7 0.33 40 0.37 0.32 0.46 10230007 26 0.35 7 0.31 33 0.35 0.31 0.41 10240001 24 0.36 4 0.33 28 0.36 0.32 0.40 10240002 37 0.32 8 0.30 45 0.32 0.30 0.36 10240003 29 0.36 17 0.33 46 0.35 0.31 0.39 10240004 3 0.52 6 0.44 9 0.46 0.43 0.54 10240005 58 0.37 36 0.34 94 0.36 0.31 0.44 10240006 29 0.37 23 0.34 52 0.36 0.33 0.39 10240007 15 0.37 44 0.34 59 0.35 0.33 0.38 10240008 34 0.37 45 0.34 79 0.35 0.33 0.38 10240009 14 0.34 17 0.32 31 0.33 0.31 0.37 10240010 30 0.35 41 0.33 71 0.34 0.32 0.38 10240011 46 0.38 16 0.32 62 0.36 0.31 0.45 10240012 38 0.36 52 0.33 90 0.34 0.32 0.38 10240013 23 0.34 26 0.31 49 0.33 0.30 0.36 10250001 16 0.37 18 0.36 34 0.37 0.35 0.39 10250002 38 0.39 40 0.40 78 0.39 0.36 0.43 10250003 25 0.37 58 0.36 83 0.36 0.33 0.38 10250004 26 0.38 10 0.37 36 0.38 0.34 0.40 10250005 33 0.38 9 0.36 42 0.38 0.35 0.42 10250006 44 0.38 16 0.36 60 0.37 0.34 0.39 10250007 5 0.37 3 0.38 8 0.37 0.36 0.39 10250008 3 0.38 4 0.36 7 0.37 0.34 0.40 10250009 15 0.39 6 0.34 21 0.37 0.33 0.42

6‐9


10250010 9 0.39 8 0.36 17 0.38 0.33 0.41 10250011 10 0.37 4 0.35 14 0.37 0.32 0.41 10250012 6 0.40 6 0.40 0.36 0.43 10250013 9 0.42 3 0.42 12 0.42 0.39 0.46 10250014 7 0.38 2 0.32 9 0.37 0.31 0.41 10250015 14 0.34 14 0.34 0.32 0.37 10250016 39 0.35 20 0.33 59 0.34 0.31 0.38 10250017 31 0.35 19 0.32 50 0.34 0.31 0.36 10260001 5 0.40 25 0.39 30 0.40 0.37 0.42 10260002 3 0.41 4 0.40 7 0.40 0.38 0.46 10260003 11 0.42 10 0.39 21 0.40 0.37 0.46 10260004 17 0.38 13 0.36 30 0.37 0.34 0.40 10260005 5 0.39 2 0.37 7 0.38 0.36 0.41 10260006 17 0.37 26 0.35 43 0.36 0.33 0.38 10260007 5 0.36 3 0.35 8 0.36 0.35 0.38 10260008 16 0.40 41 0.37 57 0.38 0.36 0.40 10260009 15 0.32 18 0.30 33 0.31 0.29 0.33 10260010 10 0.36 26 0.33 36 0.34 0.32 0.37 10260011 11 0.36 18 0.33 29 0.34 0.31 0.37 10260012 17 0.37 9 0.36 26 0.37 0.34 0.40 10260013 8 0.37 15 0.33 23 0.34 0.32 0.37 10260014 5 0.39 4 0.37 9 0.38 0.35 0.41 10260015 17 0.35 16 0.33 33 0.34 0.31 0.37 10270101 1 0.39 1 0.39 0.39 0.39 10270102 19 0.37 30 0.33 49 0.35 0.32 0.40 10270103 42 0.37 39 0.34 81 0.36 0.33 0.38 10270104 50 0.36 11 0.33 61 0.35 0.32 0.41 10270201 33 0.39 1 0.34 34 0.39 0.34 0.43 10270202 25 0.40 18 0.36 43 0.38 0.35 0.42 10270203 41 0.38 1 0.32 42 0.38 0.33 0.42 10270204 18 0.37 2 0.33 20 0.37 0.33 0.41 10270205 24 0.40 31 0.37 55 0.38 0.36 0.41 10270206 61 0.36 2 0.35 63 0.36 0.31 0.40 10270207 22 0.36 18 0.34 40 0.35 0.32 0.37 10280101 56 0.32 245 0.30 301 0.31 0.29 0.35 10280102 26 0.35 154 0.30 180 0.30 0.28 0.34 10280103 31 0.35 153 0.31 184 0.32 0.30 0.36 10280201 22 0.36 56 0.32 78 0.33 0.31 0.37 10280202 14 0.37 38 0.33 52 0.34 0.30 0.38 10280203 8 0.36 12 0.33 20 0.34 0.31 0.38 10290101 20 0.35 15 0.33 35 0.34 0.32 0.36 10290102 20 0.38 32 0.37 52 0.37 0.35 0.41

6‐10


10290103 8 0.39 9 0.37 17 0.38 0.37 0.40 10290104 15 0.40 24 0.38 39 0.39 0.37 0.42 10290105 9 0.39 11 0.37 20 0.38 0.36 0.42 10290106 5 0.36 5 0.36 10 0.36 0.35 0.39 10290108 25 0.35 24 0.34 49 0.34 0.33 0.37 10290109 2 0.37 2 0.37 0.36 0.37 10290111 1 0.36 1 0.36 0.36 0.36 10290201 1 0.36 1 0.36 0.36 0.36 10290203 1 0.35 1 0.35 0.35 0.35 10300101 54 0.34 36 0.30 90 0.32 0.30 0.40 10300102 32 0.37 36 0.33 68 0.35 0.31 0.40 10300103 22 0.38 6 0.36 28 0.38 0.35 0.42 10300104 33 0.36 12 0.34 45 0.35 0.33 0.42 10300200 18 0.34 15 0.31 33 0.33 0.30 0.41

6‐11

0.8

Sedi

men

t Del

iver

y R

atio

0.7

0.6

0.5

0.4

0.3

0.2

0.1


Figure 6-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Missouri River Basin.

Missouri River Basin


1002

0003

1003

0103

1003

0204

1004

0105

1004

0205

1005

0008

1005

0014

1006

0004

1007

0006

1008

0011

1009

0209

1011

0101

1011

0205

1012

0111

1013

0102

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0001

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0102

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0004

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0003

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0002

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0008

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0014

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0003

1026

0009

1026

0015

1027

0202

1028

0101

1029

0101

1029

0108

1030

0102

HUC8

6‐12


Table 6-2. Mean and percentiles of sediment delivery ratio (ratio of sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Missouri River Basin.

HUC Subbasin

Number_of non-cropland

HRUs simulated

within SWAT

Mean SDR 10th

Percentile SDR

90th

Percentile SDR

10010001 1 23 0.45 0.40 0.53 10010002 2 41 0.32 0.28 0.37 10020001 3 54 0.21 0.14 0.27 10020002 4 56 0.22 0.16 0.28 10020003 5 58 0.23 0.17 0.28 10020004 6 53 0.20 0.12 0.28 10020005 7 52 0.29 0.23 0.34 10020006 8 47 0.24 0.17 0.32 10020007 9 41 0.20 0.12 0.32 10020008 10 55 0.21 0.14 0.26 10030101 11 35 0.22 0.12 0.33 10030102 12 36 0.33 0.26 0.40 10030103 13 50 0.22 0.15 0.31 10030104 14 41 0.25 0.18 0.32 10030105 15 45 0.26 0.18 0.34 10030201 16 43 0.29 0.23 0.37 10030202 17 39 0.27 0.21 0.35 10030203 18 25 0.22 0.12 0.43 10030204 19 34 0.26 0.16 0.37 10030205 20 27 0.25 0.15 0.41 10040101 21 37 0.32 0.27 0.39 10040102 22 34 0.27 0.19 0.36 10040103 23 32 0.25 0.17 0.34 10040104 24 34 0.24 0.13 0.35 10040105 25 39 0.25 0.17 0.32 10040106 26 35 0.25 0.16 0.37 10040201 27 36 0.23 0.14 0.33 10040202 28 52 0.22 0.15 0.29 10040203 29 38 0.26 0.18 0.36 10040204 30 46 0.24 0.16 0.33 10040205 31 44 0.26 0.19 0.35 10050001 32 37 0.30 0.24 0.40 10050002 33 25 0.27 0.15 0.40 10050003 34 8 0.53 0.42 0.86 10050004 35 38 0.29 0.22 0.36 10050005 36 29 0.29 0.20 0.41 10050006 37 20 0.32 0.21 0.52 10050007 38 23 0.35 0.25 0.53 10050008 39 27 0.31 0.22 0.43

6‐13


10050009 40 35 0.32 0.24 0.43 10050010 41 28 0.24 0.14 0.41 10050011 42 24 0.27 0.17 0.48 10050012 43 38 0.26 0.17 0.35 10050013 44 25 0.29 0.21 0.43 10050014 45 41 0.23 0.14 0.34 10050015 46 33 0.26 0.17 0.38 10050016 47 26 0.27 0.18 0.47 10060001 48 37 0.24 0.14 0.32 10060002 49 38 0.23 0.14 0.30 10060003 50 23 0.27 0.18 0.45 10060004 51 30 0.25 0.16 0.35 10060005 52 31 0.29 0.20 0.40 10060006 53 21 0.23 0.11 0.46 10060007 54 20 0.30 0.21 0.49 10070001 55 53 0.25 0.18 0.29 10070002 56 37 0.26 0.18 0.36 10070003 57 49 0.27 0.21 0.33 10070004 58 39 0.25 0.18 0.32 10070005 59 52 0.25 0.19 0.31 10070006 60 51 0.22 0.16 0.27 10070007 61 42 0.24 0.16 0.31 10070008 62 44 0.27 0.21 0.35 10080001 63 50 0.28 0.20 0.37 10080002 64 41 0.35 0.24 0.49 10080003 65 42 0.30 0.25 0.39 10080004 66 36 0.29 0.19 0.46 10080005 67 44 0.31 0.24 0.44 10080006 68 45 0.24 0.19 0.31 10080007 69 49 0.24 0.16 0.30 10080008 70 59 0.22 0.15 0.29 10080009 71 55 0.23 0.16 0.28 10080010 72 53 0.33 0.28 0.41 10080011 73 36 0.27 0.21 0.42 10080012 74 51 0.24 0.18 0.31 10080013 75 56 0.23 0.18 0.30 10080014 76 55 0.26 0.20 0.33 10080015 77 51 0.23 0.15 0.31 10080016 78 54 0.24 0.16 0.31 10090101 79 43 0.25 0.17 0.32 10090102 80 35 0.22 0.13 0.41 10090201 81 46 0.30 0.23 0.37 10090202 82 53 0.21 0.13 0.27 10090203 83 46 0.23 0.15 0.32 10090204 84 34 0.27 0.19 0.36 10090205 85 38 0.26 0.17 0.36 10090206 86 52 0.25 0.17 0.32 10090207 87 55 0.22 0.15 0.27

6‐14


10090208 88 54 0.22 0.14 0.28 10090209 89 56 0.21 0.14 0.26 10090210 90 47 0.23 0.15 0.30 10100001 91 34 0.23 0.12 0.34 10100002 92 34 0.25 0.16 0.34 10100003 93 48 0.22 0.14 0.29 10100004 94 30 0.22 0.10 0.35 10100005 95 50 0.23 0.15 0.29 10110101 96 28 0.24 0.15 0.40 10110102 97 29 0.24 0.14 0.39 10110201 98 42 0.21 0.12 0.30 10110202 99 51 0.22 0.14 0.29 10110203 100 46 0.20 0.11 0.27 10110204 101 33 0.23 0.14 0.36 10110205 102 42 0.20 0.10 0.28 10120101 103 38 0.27 0.19 0.36 10120102 104 24 0.28 0.19 0.47 10120103 105 47 0.24 0.16 0.29 10120104 106 43 0.30 0.23 0.35 10120105 107 35 0.27 0.19 0.39 10120106 108 46 0.28 0.20 0.35 10120107 109 53 0.24 0.18 0.30 10120108 110 34 0.29 0.21 0.38 10120109 111 48 0.24 0.16 0.31 10120110 112 27 0.26 0.17 0.46 10120111 113 41 0.24 0.14 0.29 10120112 114 41 0.25 0.17 0.34 10120113 115 44 0.22 0.13 0.31 10120201 116 47 0.21 0.11 0.30 10120202 117 55 0.20 0.13 0.26 10120203 118 48 0.31 0.26 0.37 10130101 119 29 0.25 0.16 0.36 10130102 120 41 0.22 0.14 0.34 10130103 121 24 0.21 0.12 0.36 10130104 122 33 0.33 0.26 0.41 10130105 123 45 0.21 0.13 0.30 10130106 124 27 0.25 0.17 0.38 10130201 125 44 0.21 0.12 0.30 10130202 126 32 0.22 0.12 0.35 10130203 127 45 0.21 0.13 0.28 10130204 128 35 0.21 0.11 0.34 10130205 129 38 0.21 0.11 0.33 10130206 130 32 0.25 0.17 0.40 10130301 131 37 0.22 0.13 0.34 10130302 132 53 0.21 0.14 0.29 10130303 133 52 0.21 0.13 0.30 10130304 134 37 0.23 0.16 0.36 10130305 135 47 0.26 0.20 0.33

6‐15


10130306 136 52 0.20 0.12 0.28 10140101 137 33 0.22 0.12 0.36 10140102 138 57 0.20 0.13 0.26 10140103 139 32 0.24 0.15 0.46 10140104 140 31 0.27 0.19 0.41 10140105 141 43 0.26 0.19 0.30 10140201 142 48 0.21 0.13 0.29 10140202 143 46 0.21 0.12 0.28 10140203 144 41 0.21 0.13 0.32 10140204 145 44 0.23 0.15 0.29 10150001 146 29 0.22 0.14 0.42 10150002 147 36 0.23 0.15 0.37 10150003 148 36 0.21 0.12 0.34 10150004 149 43 0.21 0.13 0.32 10150005 150 27 0.26 0.18 0.44 10150006 151 39 0.22 0.13 0.34 10150007 152 41 0.24 0.16 0.32 10160001 153 29 0.25 0.16 0.40 10160002 154 35 0.23 0.14 0.35 10160003 155 29 0.26 0.17 0.43 10160004 156 51 0.25 0.20 0.32 10160005 157 31 0.27 0.20 0.38 10160006 158 39 0.25 0.18 0.34 10160007 159 30 0.38 0.33 0.56 10160008 160 45 0.24 0.17 0.33 10160009 161 43 0.24 0.17 0.35 10160010 162 29 0.29 0.22 0.42 10160011 163 39 0.25 0.17 0.36 10170101 164 30 0.24 0.15 0.41 10170102 165 29 0.22 0.12 0.43 10170103 166 24 0.30 0.22 0.52 10170201 167 26 0.24 0.15 0.50 10170202 168 32 0.28 0.20 0.37 10170203 169 25 0.21 0.12 0.51 10170204 170 25 0.22 0.13 0.46 10180001 171 46 0.25 0.17 0.32 10180002 172 53 0.21 0.13 0.27 10180003 173 44 0.27 0.19 0.36 10180004 174 46 0.30 0.24 0.35 10180005 175 36 0.28 0.20 0.38 10180006 176 54 0.20 0.12 0.29 10180007 177 47 0.23 0.17 0.31 10180008 178 53 0.21 0.14 0.28 10180009 179 33 0.26 0.19 0.39 10180010 180 44 0.23 0.17 0.32 10180011 181 48 0.25 0.20 0.30 10180012 182 39 0.24 0.16 0.34 10180013 183 38 0.25 0.18 0.40

6‐16


10180014 184 32 0.23 0.15 0.44 10190001 185 47 0.24 0.15 0.32 10190002 186 52 0.24 0.16 0.30 10190003 187 42 0.24 0.16 0.32 10190004 188 39 0.28 0.22 0.37 10190005 189 40 0.31 0.27 0.38 10190006 190 39 0.28 0.22 0.36 10190007 191 41 0.25 0.17 0.31 10190008 192 29 0.32 0.24 0.42 10190009 193 40 0.25 0.18 0.34 10190010 194 31 0.28 0.21 0.44 10190011 195 39 0.23 0.15 0.34 10190012 196 28 0.24 0.16 0.44 10190013 197 30 0.25 0.16 0.44 10190014 198 31 0.25 0.18 0.44 10190015 199 29 0.25 0.18 0.45 10190016 200 31 0.25 0.17 0.42 10190017 201 26 0.31 0.23 0.49 10190018 202 28 0.24 0.15 0.43 10200101 203 31 0.23 0.13 0.41 10200102 204 29 0.25 0.16 0.45 10200103 205 27 0.25 0.15 0.42 10200201 206 27 0.24 0.13 0.39 10200202 207 31 0.30 0.22 0.41 10200203 208 30 0.25 0.16 0.38 10210001 209 24 0.19 0.11 0.47 10210002 210 24 0.20 0.14 0.45 10210003 211 41 0.21 0.12 0.35 10210004 212 37 0.20 0.11 0.35 10210005 213 24 0.24 0.16 0.55 10210006 214 32 0.20 0.11 0.40 10210007 215 40 0.23 0.14 0.35 10210008 216 28 0.22 0.13 0.44 10210009 217 30 0.22 0.12 0.38 10210010 218 33 0.21 0.12 0.38 10220001 219 35 0.22 0.11 0.35 10220002 220 27 0.26 0.17 0.42 10220003 221 21 0.23 0.12 0.55 10220004 222 20 0.20 0.11 0.59 10230001 223 24 0.22 0.11 0.40 10230002 224 27 0.23 0.11 0.39 10230003 225 21 0.22 0.09 0.50 10230004 226 23 0.24 0.14 0.47 10230005 227 24 0.24 0.11 0.41 10230006 228 31 0.24 0.15 0.36 10230007 229 24 0.24 0.13 0.46 10240001 230 33 0.23 0.14 0.37 10240002 231 24 0.20 0.10 0.49

6‐17


10240003 232 29 0.22 0.13 0.37 10240004 233 30 0.38 0.31 0.47 10240005 234 27 0.23 0.14 0.46 10240006 235 32 0.23 0.14 0.39 10240007 236 41 0.22 0.13 0.33 10240008 237 34 0.22 0.13 0.38 10240009 238 40 0.21 0.13 0.30 10240010 239 37 0.22 0.14 0.37 10240011 240 42 0.23 0.14 0.32 10240012 241 44 0.22 0.15 0.34 10240013 242 44 0.21 0.12 0.30 10250001 243 23 0.24 0.15 0.43 10250002 244 26 0.26 0.18 0.49 10250003 245 27 0.24 0.13 0.37 10250004 246 35 0.24 0.16 0.31 10250005 247 27 0.23 0.13 0.45 10250006 248 19 0.24 0.15 0.61 10250007 249 21 0.23 0.14 0.40 10250008 250 28 0.25 0.16 0.44 10250009 251 36 0.25 0.16 0.34 10250010 252 23 0.25 0.15 0.49 10250011 253 20 0.25 0.14 0.52 10250012 254 23 0.23 0.13 0.38 10250013 255 20 0.26 0.17 0.46 10250014 256 19 0.22 0.13 0.68 10250015 257 25 0.23 0.12 0.41 10250016 258 34 0.23 0.13 0.33 10250017 259 32 0.23 0.12 0.38 10260001 260 27 0.26 0.16 0.45 10260002 261 25 0.24 0.14 0.43 10260003 262 34 0.27 0.18 0.36 10260004 263 23 0.24 0.13 0.43 10260005 264 25 0.24 0.14 0.46 10260006 265 30 0.24 0.14 0.38 10260007 266 26 0.23 0.13 0.44 10260008 267 33 0.26 0.17 0.37 10260009 268 31 0.21 0.09 0.33 10260010 269 37 0.22 0.12 0.32 10260011 270 27 0.23 0.13 0.47 10260012 271 30 0.25 0.15 0.39 10260013 272 28 0.24 0.12 0.40 10260014 273 28 0.26 0.16 0.38 10260015 274 29 0.23 0.12 0.37 10270101 275 35 0.26 0.20 0.40 10270102 276 48 0.22 0.14 0.28 10270103 277 48 0.22 0.14 0.30 10270104 278 60 0.20 0.14 0.26 10270201 279 22 0.24 0.14 0.39

6‐18


10270202 280 28 0.26 0.17 0.41 10270203 281 22 0.24 0.14 0.53 10270204 282 24 0.24 0.14 0.47 10270205 283 37 0.25 0.18 0.35 10270206 284 28 0.23 0.12 0.38 10270207 285 37 0.22 0.13 0.36 10280101 286 41 0.20 0.11 0.28 10280102 287 42 0.20 0.11 0.28 10280103 288 48 0.21 0.13 0.31 10280201 289 43 0.22 0.13 0.29 10280202 290 42 0.22 0.14 0.33 10280203 291 46 0.22 0.14 0.30 10290101 292 52 0.20 0.13 0.31 10290102 293 58 0.22 0.15 0.28 10290103 294 27 0.24 0.16 0.48 10290104 295 57 0.23 0.16 0.30 10290105 296 55 0.23 0.17 0.30 10290106 297 67 0.20 0.13 0.26 10290107 298 62 0.20 0.12 0.27 10290108 299 59 0.21 0.14 0.26 10290109 300 54 0.22 0.16 0.29 10290110 301 60 0.21 0.14 0.27 10290111 302 63 0.20 0.13 0.27 10290201 303 63 0.19 0.14 0.24 10290202 304 49 0.21 0.14 0.30 10290203 305 46 0.21 0.13 0.30 10300101 306 46 0.20 0.11 0.31 10300102 307 55 0.21 0.14 0.28 10300103 308 48 0.23 0.16 0.31 10300104 309 48 0.22 0.13 0.30 10300200 310 48 0.20 0.11 0.29

6‐19


Figure 6-3. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Missouri River Basin.

Missouri River Basin

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

1001

0001

1003

0101

1004

0101

1004

0205

1005

0010

1006

0004

1007

0007

1008

0009

1009

0201

1010

0001

1011

0204

1012

0109

1013

0103

1013

0301

1014

0105

1015

0006

1016

0009

1018

0001

1018

0011

1019

0007

1019

0017

1021

0003

1022

0003

1024

0002

1024

0012

1025

0009

1026

0002

1026

0012

1027

0203

1028

0203

1029

0110

HUC8

Sedi

men

t Del

iver

y R

atio


6‐20

Chapter 7

Delivery Ratio used in CEAP Cropland Modeling in the Arkansas-White-Red River

Basin

7‐1

Delivery Ratio used in CEAP in the Arkansas White Red River Basin

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nutrients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009) in the Arkansas White Red River Basin. APEX simulates all of the basic biological, chemical, hydrological, and meteorological processes of farming systems and their interactions. Soil erosion is simulated over time, including wind erosion, sheet and rill erosion. The nitrogen, phosphorus, and carbon cycles are simulated, including chemical transformations in the soil that affect their availability for plant growth or for transport from the field.



Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the deposition is temporary. Eroded soil may deposit in lower spots, flatter lands, deposited at the edge of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary stream channels during transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National Assessment modeling. The SDR used in this

study is a function of the ratio of the time of concentration for the HRU (land uses other than cultivated cropland) or field (cultivated cropland) to the time of concentration for the watershed (8-digit HUC). The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to the time the surface water runoff reaches the outlet of the watershed. It is calculated by summing the overland flow time (the time it takes for flow from the remotest point in the watershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream channels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concentration for the HRU is derived from characteristics of the watershed, the HRU, and the proportion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique delivery ratio within each watershed, as does each HRU. The description of the sediment delivery ratio procedure is provided in Chapter 1.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE developed from Theory) (Williams, 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to determine the amount of sediment that reaches the 8-digit watershed outlet from each APEX simulation site. The sediment load from apex simulation sites are aggregated for the 8-digit watershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality effects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimating the SDR for each HRU, the SDR is applied to determine the amount of sediment that reaches the 8-digit watershed outlet.

Sediment delivery ratios were estimated to account for sediment losses or deposition occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated cropland and CRP and non-cropland HRUs in the Arkansas-White-Red River Basin (Figure 7-1). The Arkansas-White-Red River Basin has a drainage area of 159 million acres. The cultivated cropland and land enrolled in the CRP General Signup is about 22% of the Arkansas-White-Red River Basin. A total of 173, 8-digit watersheds are in the Arkansas-White-Red River Basin (Figure 7-1). Within each 8-digit

7‐2

watershed, the percent of cultivated cropland and CRP area and non-cultivated cropland area varies widely across the entire basin.

A total of 3155 representative cultivated fields (1280 NRI-CEAP cropland points and 1875 CRP points) were setup to run using APEX. Thirty-six out of 173, 8-digit watersheds in the Arkansas-White-Red River Basin have no CEAP points; the thirty-six 8-digit watersheds have 0.01% to 6.2% of land cultivated.

Non-cultivated land is distributed over 78% of the Arkansas-White-Red River Basin. Within each 8-digit watershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 6,968 HRUs are simulated in SWAT for the Arkansas-White-Red River Basin.

Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each cultivated cropland site simulated in an 8-digit watershed and so as for HRU. The number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit watersheds in the Arkansas-White_Red River Basin are shown in Table 7-1 and Figure 7-2. Table 7-2 shows number of HRUs and mean, 10th percentile and 90th percentile of the SDRs estimated for the non-cultivated land HRUs in the 8-digit watersheds in the Arkansas-White-RedRiver Basin. The mean, 10th and 90th percentile SDRs for the non-cropland HRUs are plotted in Figure 7-3.

In addition to SDR, an enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sediment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the outlet. The enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed outlet. The enrichment ratio is estimated for each APEX simulation site and SWAT HRUs and it varies from 0.5 to 1.5 (Average 1.0). As sediment is transported from the edge-of-field to the watershed outlet, coarse sediments are deposited first while more of the fine sediment that hold organic particles remain in suspension,


thus enriching the organic concentrations delivered to the watershed outlet.


7‐3


Figure 8-1. Map of the 8-digit watersheds in the Arkansas-White-Red River Basin

7‐4


Table 7-1. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Arkansas-White-Red River Basin.

HUC

Cropland CRP Crop + CRP

Points Mean_

SDR Points

Mean_

SDR Points

Mean_

SDR

10th

percentile 90th

percentile

11010004 3 0.37 3 0.37 0.37 0.39 11010007 19 0.37 19 0.37 0.32 0.42 11010008 5 0.39 5 0.39 0.38 0.41 11010009 7 0.50 1 0.40 8 0.49 0.40 0.56 11010013 11 0.42 2 0.39 13 0.42 0.39 0.47 11010014 1 0.43 4 0.37 5 0.39 0.36 0.43 11020002 1 0.40 1 0.40 0.40 0.40 11020005 7 0.44 36 0.40 43 0.41 0.38 0.44 11020006 1 0.42 1 0.42 0.42 0.42 11020008 1 0.43 16 0.43 17 0.43 0.38 0.49 11020009 15 0.41 49 0.40 64 0.40 0.38 0.43 11020010 1 0.40 1 0.40 0.40 0.40 11020011 4 0.39 12 0.38 16 0.38 0.35 0.40 11020012 8 0.37 18 0.37 26 0.37 0.35 0.39 11020013 2 0.37 11 0.38 13 0.38 0.36 0.42 11030001 16 0.40 69 0.39 85 0.39 0.36 0.44 11030002 11 0.40 36 0.40 47 0.40 0.37 0.43 11030003 8 0.38 5 0.36 13 0.37 0.34 0.43 11030004 27 0.38 41 0.36 68 0.37 0.33 0.42 11030005 18 0.39 49 0.36 67 0.37 0.34 0.40 11030006 10 0.41 12 0.39 22 0.40 0.37 0.42 11030007 12 0.41 18 0.41 30 0.41 0.36 0.49 11030008 9 0.37 9 0.35 18 0.36 0.34 0.39 11030009 29 0.36 40 0.34 69 0.35 0.31 0.38 11030010 11 0.45 10 0.44 21 0.45 0.39 0.50 11030011 17 0.36 9 0.38 26 0.37 0.35 0.39 11030012 21 0.39 3 0.40 24 0.39 0.35 0.43 11030013 12 0.40 3 0.42 15 0.40 0.37 0.45 11030014 23 0.36 57 0.36 80 0.36 0.34 0.39 11030015 16 0.37 48 0.35 64 0.35 0.33 0.38 11030016 9 0.41 9 0.41 0.38 0.46 11030017 4 0.40 4 0.40 0.39 0.42 11030018 5 0.36 5 0.36 0.35 0.38 11040001 3 0.41 3 0.41 0.41 0.42 11040002 11 0.37 25 0.37 36 0.37 0.34 0.40 11040003 10 0.42 48 0.41 58 0.41 0.38 0.46 11040004 8 0.40 24 0.40 32 0.40 0.38 0.41 11040005 17 0.38 54 0.37 71 0.37 0.35 0.38 11040006 26 0.38 73 0.37 99 0.37 0.34 0.40 11040007 23 0.39 32 0.36 55 0.37 0.33 0.41 11040008 25 0.40 48 0.38 73 0.39 0.37 0.41 11050001 27 0.34 6 0.34 33 0.34 0.32 0.36

7‐5


11050002 41 0.35 1 0.34 42 0.35 0.33 0.36 11050003 3 0.37 3 0.37 0.36 0.40 11060001 1 0.35 1 0.35 0.35 0.35 11060002 5 0.39 23 0.37 28 0.38 0.35 0.40 11060003 12 0.40 18 0.37 30 0.38 0.35 0.43 11060004 21 0.36 13 0.32 34 0.34 0.31 0.37 11060005 32 0.35 15 0.33 47 0.34 0.32 0.36 11060006 14 0.36 14 0.36 0.32 0.42 11070101 1 0.33 8 0.34 9 0.34 0.33 0.35 11070102 4 0.41 2 0.37 6 0.39 0.36 0.42 11070103 10 0.37 2 0.35 12 0.36 0.35 0.39 11070104 5 0.41 1 0.38 6 0.40 0.38 0.44 11070105 2 0.40 2 0.40 0.37 0.42 11070106 6 0.37 5 0.33 11 0.35 0.31 0.41 11070201 11 0.40 4 0.36 15 0.39 0.35 0.46 11070202 9 0.41 7 0.39 16 0.40 0.37 0.44 11070203 2 0.37 1 0.37 3 0.37 0.36 0.38 11070204 21 0.40 4 0.37 25 0.39 0.37 0.46 11070205 17 0.39 2 0.37 19 0.39 0.36 0.43 11070206 1 0.43 1 0.43 0.43 0.43 11070207 30 0.36 23 0.35 53 0.36 0.33 0.38 11070208 1 0.41 1 0.41 0.41 0.41 11070209 3 0.36 3 0.36 0.33 0.41 11080006 2 0.40 17 0.38 19 0.38 0.36 0.40 11080007 1 0.41 13 0.39 14 0.39 0.38 0.41 11080008 1 0.44 1 0.44 0.44 0.44 11090101 1 0.41 9 0.32 10 0.33 0.25 0.41 11090102 2 0.44 3 0.40 5 0.42 0.38 0.48 11090103 5 0.41 12 0.34 17 0.36 0.26 0.43 11090104 10 0.41 8 0.39 18 0.40 0.36 0.44 11090105 7 0.43 9 0.27 16 0.34 0.24 0.47 11090106 7 0.40 10 0.26 17 0.32 0.22 0.42 11090201 21 0.33 11 0.31 32 0.33 0.30 0.35 11090202 6 0.34 2 0.31 8 0.33 0.31 0.37 11100101 18 0.39 56 0.37 74 0.38 0.25 0.43 11100102 17 0.43 29 0.42 46 0.43 0.39 0.48 11100103 16 0.39 39 0.26 55 0.30 0.22 0.40 11100104 32 0.40 13 0.24 45 0.35 0.23 0.42 11100201 17 0.37 19 0.28 36 0.33 0.22 0.41 11100202 10 0.45 12 0.27 22 0.36 0.23 0.47 11100203 9 0.39 21 0.32 30 0.34 0.23 0.39 11100301 20 0.32 11 0.30 31 0.32 0.29 0.35 11100302 1 0.38 1 0.38 0.38 0.38 11100303 1 0.34 1 0.32 2 0.33 0.32 0.34 11110102 1 0.44 2 0.46 3 0.46 0.44 0.48 11110103 1 0.40 1 0.40 0.40 0.40 11110104 1 0.47 1 0.47 0.47 0.47 11110201 3 0.43 3 0.43 0.42 0.44 11110202 3 0.42 1 0.36 4 0.41 0.36 0.47 11110203 4 0.48 2 0.45 6 0.47 0.41 0.48 11110205 1 0.46 3 0.43 4 0.44 0.42 0.46

7‐6


11110206 2 0.36 2 0.36 0.35 0.37 11110207 2 0.39 1 0.39 3 0.39 0.39 0.39 11120101 19 0.40 92 0.31 111 0.32 0.24 0.40 11120102 8 0.41 44 0.27 52 0.29 0.23 0.40 11120103 9 0.42 39 0.34 48 0.36 0.24 0.46 11120104 17 0.43 43 0.35 60 0.37 0.27 0.46 11120105 14 0.41 37 0.25 51 0.29 0.22 0.41 11120201 7 0.44 7 0.34 14 0.39 0.26 0.46 11120202 11 0.37 48 0.31 59 0.32 0.20 0.37 11120301 10 0.42 21 0.35 31 0.37 0.27 0.44 11120302 12 0.37 31 0.28 43 0.30 0.19 0.37 11120303 15 0.36 10 0.36 25 0.36 0.33 0.39 11120304 13 0.42 24 0.33 37 0.36 0.24 0.43 11130101 25 0.38 22 0.30 47 0.34 0.22 0.39 11130102 12 0.40 1 0.26 13 0.39 0.30 0.46 11130103 14 0.41 37 0.30 51 0.33 0.23 0.45 11130104 6 0.44 23 0.27 29 0.31 0.24 0.44 11130105 6 0.37 6 0.21 12 0.29 0.21 0.38 11130201 4 0.37 5 0.27 9 0.32 0.18 0.42 11130202 12 0.38 1 0.44 13 0.39 0.36 0.45 11130203 16 0.38 9 0.37 25 0.37 0.35 0.41 11130204 3 0.41 11 0.24 14 0.28 0.21 0.43 11130205 1 0.25 1 0.25 0.25 0.25 11130206 6 0.40 6 0.40 0.39 0.43 11130207 5 0.39 3 0.22 8 0.33 0.22 0.40 11130208 2 0.37 2 0.39 4 0.38 0.34 0.41 11130209 7 0.37 7 0.37 0.35 0.39 11130210 3 0.39 1 0.37 4 0.39 0.37 0.42 11130301 6 0.38 14 0.25 20 0.29 0.21 0.41 11130302 27 0.34 2 0.32 29 0.33 0.31 0.39 11130303 2 0.36 2 0.36 0.36 0.36 11130304 3 0.39 3 0.39 0.39 0.40 11140101 4 0.38 1 0.19 5 0.34 0.19 0.39 11140102 4 0.36 4 0.36 0.35 0.37 11140104 1 0.44 1 0.44 0.44 0.44 11140106 2 0.39 9 0.39 11 0.39 0.35 0.43 11140109 1 0.36 1 0.36 0.36 0.36 11140201 5 0.44 5 0.44 0.44 0.44 11140202 1 0.44 1 0.44 0.44 0.44 11140206 2 0.43 2 0.48 4 0.46 0.42 0.50 11140207 2 0.39 2 0.39 0.38 0.40 11140301 10 0.38 5 0.22 15 0.32 0.21 0.42 11140302 1 0.38 3 0.24 4 0.28 0.22 0.38 11140304 2 0.43 3 0.44 5 0.43 0.41 0.45

7‐7


Table 7-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Arkansas-White-Red River Basin

HUC Subbasin

Number_of non-cropland HRUs simulated within

SWAT

Mean SDR 10th

Percentile SDR

90th

Percentile SDR

11010001 1 51 0.18 0.08 0.28 11010002 2 65 0.18 0.11 0.26 11010003 3 61 0.17 0.09 0.25 11010004 4 52 0.18 0.08 0.26 11010005 5 48 0.19 0.11 0.26 11010006 6 65 0.19 0.12 0.26 11010007 7 41 0.21 0.13 0.33 11010008 8 50 0.20 0.10 0.29 11010009 9 38 0.33 0.22 0.57 11010010 10 52 0.20 0.13 0.30 11010011 11 55 0.19 0.11 0.29 11010012 12 60 0.20 0.13 0.27 11010013 13 34 0.29 0.10 0.45 11010014 14 52 0.19 0.12 0.28 11020001 15 40 0.19 0.07 0.30 11020002 16 49 0.20 0.11 0.27 11020003 17 33 0.21 0.06 0.36 11020004 18 25 0.26 0.14 0.45 11020005 19 25 0.27 0.18 0.39 11020006 20 34 0.22 0.10 0.33 11020007 21 22 0.24 0.12 0.51 11020008 22 24 0.27 0.15 0.46 11020009 23 28 0.26 0.17 0.43 11020010 24 46 0.19 0.08 0.29 11020011 25 33 0.24 0.13 0.36 11020012 26 23 0.24 0.14 0.48 11020013 27 26 0.23 0.13 0.40 11030001 28 23 0.26 0.16 0.46 11030002 29 21 0.25 0.16 0.54 11030003 30 18 0.24 0.17 0.53 11030004 31 25 0.26 0.16 0.44 11030005 32 24 0.24 0.14 0.49 11030006 33 22 0.27 0.18 0.50 11030007 34 25 0.27 0.19 0.41 11030008 35 27 0.25 0.15 0.37 11030009 36 23 0.26 0.15 0.54 11030010 37 22 0.39 0.30 0.55 11030011 38 28 0.25 0.15 0.37 11030012 39 27 0.27 0.17 0.40 11030013 40 33 0.31 0.23 0.41 11030014 41 24 0.26 0.17 0.52

7‐8


11030015 42 25 0.25 0.15 0.44 11030016 43 24 0.31 0.21 0.47 11030017 44 34 0.32 0.25 0.39 11030018 45 34 0.25 0.14 0.37 11040001 46 54 0.20 0.13 0.27 11040002 47 32 0.22 0.13 0.39 11040003 48 21 0.26 0.17 0.42 11040004 49 25 0.25 0.16 0.40 11040005 50 22 0.22 0.13 0.42 11040006 51 24 0.23 0.15 0.47 11040007 52 23 0.23 0.15 0.46 11040008 53 29 0.25 0.16 0.44 11050001 54 46 0.21 0.13 0.30 11050002 55 41 0.22 0.12 0.30 11050003 56 51 0.20 0.11 0.28 11060001 57 37 0.21 0.12 0.33 11060002 58 34 0.24 0.16 0.36 11060003 59 32 0.23 0.14 0.42 11060004 60 28 0.24 0.14 0.42 11060005 61 30 0.23 0.14 0.37 11060006 62 44 0.21 0.11 0.30 11070101 63 48 0.21 0.13 0.31 11070102 64 41 0.23 0.15 0.34 11070103 65 58 0.21 0.15 0.28 11070104 66 48 0.24 0.16 0.31 11070105 67 54 0.24 0.20 0.31 11070106 68 52 0.19 0.12 0.30 11070107 69 50 0.20 0.13 0.27 11070201 70 47 0.24 0.19 0.32 11070202 71 35 0.27 0.20 0.39 11070203 72 32 0.23 0.15 0.44 11070204 73 65 0.23 0.18 0.30 11070205 74 69 0.23 0.18 0.29 11070206 75 60 0.28 0.21 0.36 11070207 76 61 0.20 0.13 0.29 11070208 77 43 0.21 0.15 0.36 11070209 78 75 0.18 0.13 0.26 11080001 79 39 0.22 0.10 0.32 11080002 80 23 0.21 0.08 0.50 11080003 81 38 0.23 0.12 0.33 11080004 82 37 0.21 0.07 0.34 11080005 83 27 0.24 0.14 0.43 11080006 84 35 0.21 0.09 0.37 11080007 85 32 0.23 0.13 0.37 11080008 86 20 0.27 0.15 0.44 11090101 87 43 0.23 0.16 0.29 11090102 88 21 0.25 0.12 0.48 11090103 89 23 0.28 0.16 0.48

7‐9


11090104 90 15 0.27 0.13 0.63 11090105 91 36 0.23 0.13 0.32 11090106 92 42 0.21 0.11 0.29 11090201 93 20 0.23 0.10 0.51 11090202 94 42 0.20 0.10 0.30 11090203 95 46 0.21 0.12 0.32 11090204 96 46 0.22 0.12 0.33 11100101 97 27 0.24 0.12 0.37 11100102 98 24 0.29 0.17 0.44 11100103 99 19 0.25 0.12 0.52 11100104 100 21 0.27 0.13 0.46 11100201 101 40 0.22 0.12 0.31 11100202 102 22 0.29 0.15 0.44 11100203 103 36 0.27 0.19 0.37 11100301 104 39 0.20 0.12 0.36 11100302 105 63 0.19 0.12 0.25 11100303 106 49 0.19 0.11 0.26 11110101 107 71 0.23 0.17 0.29 11110102 108 71 0.27 0.19 0.32 11110103 109 82 0.17 0.11 0.23 11110104 110 64 0.24 0.19 0.31 11110105 111 64 0.16 0.08 0.25 11110201 112 66 0.21 0.14 0.29 11110202 113 68 0.19 0.13 0.27 11110203 114 78 0.25 0.20 0.32 11110204 115 69 0.17 0.11 0.25 11110205 116 73 0.22 0.18 0.27 11110206 117 60 0.16 0.08 0.26 11110207 118 46 0.29 0.20 0.37 11120101 119 22 0.26 0.15 0.48 11120102 120 17 0.27 0.16 0.58 11120103 121 30 0.24 0.14 0.36 11120104 122 20 0.27 0.13 0.54 11120105 123 32 0.25 0.16 0.37 11120201 124 25 0.27 0.18 0.37 11120202 125 21 0.25 0.13 0.48 11120301 126 21 0.26 0.14 0.53 11120302 127 33 0.23 0.12 0.35 11120303 128 28 0.24 0.13 0.38 11120304 129 28 0.25 0.15 0.41 11130101 130 25 0.28 0.17 0.42 11130102 131 25 0.27 0.16 0.38 11130103 132 30 0.24 0.15 0.36 11130104 133 33 0.24 0.15 0.35 11130105 134 17 0.26 0.13 0.59 11130201 135 47 0.21 0.12 0.30 11130202 136 36 0.23 0.13 0.35 11130203 137 34 0.24 0.15 0.36

7‐10


11130204 138 22 0.27 0.16 0.41 11130205 139 20 0.25 0.13 0.43 11130206 140 44 0.26 0.20 0.35 11130207 141 35 0.23 0.15 0.36 11130208 142 34 0.24 0.15 0.36 11130209 143 42 0.23 0.15 0.33 11130210 144 56 0.23 0.16 0.29 11130301 145 37 0.22 0.12 0.32 11130302 146 32 0.21 0.10 0.33 11130303 147 46 0.20 0.11 0.30 11130304 148 50 0.24 0.18 0.31 11140101 149 55 0.24 0.19 0.29 11140102 150 40 0.23 0.17 0.34 11140103 151 58 0.21 0.15 0.27 11140104 152 60 0.21 0.15 0.27 11140105 153 56 0.18 0.10 0.24 11140106 154 61 0.24 0.18 0.30 11140107 155 54 0.21 0.15 0.28 11140108 156 54 0.19 0.13 0.28 11140109 157 55 0.24 0.16 0.32 11140201 158 58 0.26 0.18 0.33 11140202 159 37 0.40 0.35 0.47 11140203 160 44 0.23 0.15 0.30 11140204 161 49 0.48 0.37 0.62 11140205 162 49 0.24 0.16 0.33 11140206 163 54 0.33 0.24 0.47 11140207 164 47 0.27 0.20 0.38 11140208 165 27 0.23 0.15 0.40 11140209 166 43 0.23 0.14 0.32 11140301 167 50 0.24 0.17 0.32 11140302 168 50 0.27 0.21 0.34 11140303 169 68 0.22 0.17 0.29 11140304 170 62 0.26 0.20 0.31 11140305 171 64 0.21 0.16 0.27 11140306 172 50 0.24 0.16 0.32 11140307 173 42 0.21 0.14 0.35

7‐11


0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

Sedi

men

t Del

iver

y R

atio

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ent D

eliv

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1101

0001

1101

0004

1101

0005

1101

0009

1101

0009

1102

0002

1102

0008

Figure 7-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Arkansas-White-Red River Basin

Arkansas-White-Red River Basin 1.0


0.8

HUC8

Figure 7-3. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Arkansas-White-Red River Basin

Arkansas-White-Red River Basin

1.0


HUC8

1101

0013

1102

0003

1102

0011

1102

0007

1103

0001

1102

0011

1103

0002

1103

0006

1103

0010

1103

0014

1103

0018

1104

0004

1103

0004

1103

0007

1103

0010

1103

0013

1103

0016

1104

0001

1104

0004

1104

0008

1104

0007

1106

0001

1105

0002

1106

0005

1106

0002

1107

0103

1106

0005

1107

0107

1107

0102

1107

0204

1107

0105

1107

0208

1107

0202

1108

0003

1107

0205

1107

0208

1108

0007

1108

0007

1109

0103

1109

0102

1109

0201

1109

0105

1110

0101

1109

0202

1110

0201

1110

0103

1110

0302

1110

0202

1111

0103

1110

0302

1111

0202

1111

0103

1111

0206

1111

0202

1112

0103

1111

0206

1112

0202

1112

0102

1112

0304

1112

0105

1113

0104

1112

0301

1113

0203

1112

0304

1113

0207

1113

0103

1113

0301

1113

0201

1114

0101

1113

0204

1114

0105

1113

0207

1114

0109

1113

0210

1114

0204

1113

0303

1114

0208

1114

0102

1114

0303

11

1401

0911

1402

0611

1403

02

7‐12

Chapter 8

Delivery Ratio used in CEAP Cropland Modeling in the Lower Mississippi River

Basin

8‐1

Delivery Ratio used in CEAP in the Lower Mississippi River Basin

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nutrients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009) in the Lower Mississippi River Basin. APEX simulates all of the basic biological, chemical, hydrological, and meteorological processes of farming systems and their interactions. Soil erosion is simulated over time, including wind erosion, sheet and rill erosion. The nitrogen, phosphorus, and carbon cycles are simulated, including chemical transformations in the soil that affect their availability for plant growth or for transport from the field.



Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the deposition is temporary. Eroded soil may deposit in lower spots, flatter lands, deposited at the edge of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary

stream channels during transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National Assessment modeling. The SDR used in this study is a function of the ratio of the time of concentration for the HRU (land uses other than cultivated cropland) or field (cultivated cropland) to the time of concentration for the watershed (8-digit HUC). The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to the time the surface water runoff reaches the outlet of the watershed. It is calculated by summing the overland flow time (the time it takes for flow from the remotest point in the watershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream channels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concentration for the HRU is derived from characteristics of the watershed, the HRU, and the proportion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique delivery ratio within each watershed, as does each HRU. The description of the sediment delivery ratio procedure is provided in Chapter 1.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE developed from Theory) (Williams, 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to determine the amount of sediment that reaches the 8-digit watershed outlet from each APEX simulation site. The sediment load from apex simulation sites are aggregated for the 8-digit watershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality effects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimating the SDR for each HRU, the SDR is applied to determine the amount of sediment that reaches the 8-digit watershed outlet.

Sediment delivery ratios were estimated to account for sediment losses or deposition occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated cropland and CRP and non-cropland HRUs in the

8‐2

Delivery Ratio used in CEAP in the Lower Mississippi River Basin

Lower Mississippi River Basin (Figure 8-1). The Lower Mississippi River Basin has a drainage area of 67 million acres. The cultivated cropland and land enrolled in the CRP General Signup is about 30% of the Lower Mississippi River Basin. A total of 82, 8-digit watersheds are in the Lower Mississippi River Basin (Figure 8-1). Within each 8-digit watershed, the percent of cultivated cropland and CRP area and non-cultivated cropland area varies widely across the entire basin.

A total of 2299 representative cultivated fields (1735 NRI-CEAP cropland points and 564 CRP points) were setup to run using APEX. Fifteen out of 82, 8-digit watersheds in the Lower Mississippi River Basin have no CEAP points; the fifteen 8-digit watersheds have zero or fewer than 6.3% of land cultivated (except for HUC 08030208, which has 31.4% of land cultivated).

Non-cultivated land is distributed over 70% of the River Basin. Within each 8-digit watershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 2,979 HRUs are simulated in SWAT for the Lower Mississippi River Basin.

Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each cultivated cropland site simulated in an 8-digit watershed and so as for HRU. The number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit watersheds in the Lower Mississippi River Basin are shown in Table 8-1 and Figure 8-2. Table 8-2 shows number of HRUs and mean, 10th percentile and 90th percentile of the SDRs estimated for the non-cultivated land HRUs in the 8-digit watersheds in the Lower Mississippi River Basin. The mean, 10th and 90th percentile SDRs for the non-cropland HRUs are plotted in Figure 8-3.

In addition to SDR, an enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sediment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the outlet. The

enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed outlet. The enrichment ratio is estimated for each APEX simulation site and SWAT HRUs and it varies from 0.5 to 1.5 (Average 1.0). As sediment is transported from the edge-of-field to the watershed outlet, coarse sediments are deposited first while more of the fine sediment that hold organic particles remain in suspension, thus enriching the organic concentrations delivered to the watershed outlet.


8‐3

Figure 8-1. Map of the 8-digit watersheds in the Lower Mississippi River Basin

8‐5

Table 8-1. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Lower Mississippi River Basin


Points Mean_S DR Points Mean_S

DR Points Mean_S DR

10th

prcentile 90th prcentile

8010100 65 0.49 8 0.46 73 0.49 0.44 0.54 8010201 94 0.40 50 0.38 144 0.39 0.35 0.44 8010202 94 0.39 27 0.34 121 0.38 0.33 0.42 8010203 52 0.38 15 0.35 67 0.37 0.34 0.40 8010204 32 0.36 12 0.34 44 0.35 0.31 0.38 8010205 32 0.36 6 0.33 38 0.36 0.32 0.42 8010206 8 0.52 8 0.52 0.44 0.53 8010207 16 0.41 22 0.37 38 0.38 0.35 0.41 8010208 66 0.35 38 0.34 104 0.35 0.31 0.38 8010209 27 0.37 4 0.37 31 0.37 0.33 0.40 8010210 8 0.37 16 0.35 24 0.36 0.32 0.41 8010211 6 0.42 6 0.42 0.38 0.44 8020100 3 0.48 3 0.48 0.47 0.51 8020201 19 0.45 19 0.45 0.41 0.49 8020203 119 0.40 7 0.36 126 0.39 0.34 0.44 8020204 83 0.40 5 0.31 88 0.40 0.35 0.42 8020205 42 0.40 4 0.38 46 0.40 0.36 0.44 8020301 10 0.42 9 0.38 19 0.40 0.33 0.45 8020302 65 0.39 3 0.36 68 0.38 0.35 0.42 8020303 40 0.41 6 0.40 46 0.41 0.38 0.43 8020304 61 0.42 61 0.42 0.39 0.46 8020401 11 0.52 1 0.51 12 0.52 0.48 0.58 8020402 18 0.42 18 0.42 0.39 0.45 8030100 3 0.51 1 0.50 4 0.51 0.48 0.54 8030201 8 0.39 32 0.36 40 0.36 0.31 0.42 8030202 61 0.46 20 0.43 81 0.45 0.41 0.49 8030203 4 0.38 8 0.38 12 0.38 0.33 0.44 8030204 66 0.40 30 0.36 96 0.38 0.33 0.42 8030205 28 0.38 30 0.37 58 0.38 0.32 0.42 8030206 32 0.41 8 0.38 40 0.40 0.37 0.44 8030207 114 0.36 14 0.37 128 0.36 0.34 0.38 8030209 27 0.47 4 0.44 31 0.47 0.43 0.51 8040102 1 0.37 1 0.37 0.37 0.37 8040103 2 0.39 1 0.35 3 0.37 0.35 0.41 8040202 1 0.39 1 0.39 0.39 0.39 8040205 12 0.45 12 0.45 0.42 0.51 8040207 2 0.55 1 0.55 3 0.55 0.55 0.55 8040301 9 0.51 1 0.46 10 0.51 0.46 0.53 8040305 2 0.53 1 0.66 3 0.57 0.51 0.66 8040306 13 0.49 1 0.55 14 0.50 0.44 0.55 8050001 57 0.38 19 0.36 76 0.37 0.35 0.41 8050002 27 0.49 11 0.49 38 0.49 0.45 0.53 8050003 36 0.42 13 0.41 49 0.42 0.37 0.46 8060100 2 0.44 1 0.41 3 0.43 0.41 0.47 8060201 7 0.38 37 0.35 44 0.35 0.32 0.37

8‐5

8060202 10 0.34 51 0.32 61 0.33 0.30 0.35 8060203 1 0.39 7 0.35 8 0.36 0.34 0.39 8060204 1 0.44 5 0.41 6 0.41 0.38 0.46 8060205 1 0.43 3 0.34 4 0.36 0.30 0.43 8060206 3 0.43 3 0.43 0.39 0.46 8070100 2 0.52 2 0.52 0.51 0.54 8070201 7 0.39 7 0.39 0.34 0.42 8070202 9 0.34 9 0.34 0.33 0.37 8070203 3 0.35 3 0.35 0.33 0.36 8070204 3 0.52 3 0.52 0.47 0.54 8070300 10 0.41 10 0.41 0.39 0.47 8080101 12 0.43 12 0.43 0.40 0.47 8080102 42 0.43 2 0.34 44 0.42 0.39 0.45 8080103 24 0.47 24 0.47 0.42 0.49 8080201 40 0.44 2 0.42 42 0.44 0.41 0.47 8080202 61 0.44 61 0.44 0.39 0.47 8080203 16 0.40 1 0.36 17 0.39 0.37 0.43 8080204 4 0.39 4 0.39 0.37 0.42 8080205 4 0.46 1 0.40 5 0.45 0.40 0.48 8080206 6 0.46 6 0.46 0.41 0.47 8090301 14 0.50 14 0.50 0.46 0.52 8090302 3 0.49 3 0.49 0.49 0.49

Table 8-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Lower Mississippi River Basin

HUC Subbasin Number_of non-cropland HRUs simulated within SWAT

Mean SDR 10th

Percentile SDR

90th

Percentile SDR

8010100 1 36 0.42 0.33 0.50 8010201 2 33 0.29 0.21 0.39 8010202 3 29 0.28 0.18 0.39 8010203 4 41 0.26 0.19 0.33 8010204 5 34 0.24 0.15 0.38 8010205 6 40 0.23 0.14 0.31 8010206 7 24 0.45 0.39 0.56 8010207 8 43 0.27 0.20 0.32 8010208 9 32 0.25 0.16 0.38 8010209 10 38 0.27 0.19 0.37 8010210 11 48 0.24 0.16 0.33 8010211 12 29 0.32 0.24 0.39 8020100 13 17 0.43 0.35 0.65 8020201 14 31 0.30 0.19 0.41 8020202 15 51 0.25 0.18 0.32 8020203 16 29 0.26 0.17 0.46 8020204 17 28 0.23 0.12 0.44

8‐5

8020205 18 33 0.26 0.17 0.38 8020301 19 35 0.29 0.20 0.38 8020302 20 25 0.26 0.13 0.43 8020303 21 29 0.29 0.21 0.41 8020304 22 28 0.29 0.17 0.44 8020401 23 17 0.48 0.40 0.61 8020402 24 28 0.31 0.21 0.40 8030100 25 22 0.46 0.38 0.59 8030201 26 32 0.25 0.16 0.39 8030202 27 28 0.37 0.24 0.54 8030203 28 44 0.25 0.17 0.33 8030204 29 28 0.27 0.16 0.40 8030205 30 36 0.25 0.16 0.34 8030206 31 33 0.28 0.18 0.40 8030207 32 29 0.25 0.15 0.44 8030208 33 28 0.46 0.38 0.59 8030209 34 30 0.40 0.34 0.48 8040101 35 56 0.23 0.16 0.29 8040102 36 41 0.26 0.19 0.33 8040103 37 56 0.24 0.19 0.31 8040201 38 41 0.27 0.21 0.35 8040202 39 43 0.35 0.29 0.41 8040203 40 48 0.24 0.18 0.29 8040204 41 46 0.25 0.18 0.33 8040205 42 41 0.32 0.26 0.37 8040206 43 43 0.24 0.16 0.32 8040207 44 35 0.41 0.33 0.49 8040301 45 33 0.41 0.34 0.52 8040302 46 41 0.27 0.19 0.37 8040303 47 43 0.25 0.18 0.33 8040304 48 43 0.29 0.22 0.37 8040305 49 14 0.61 0.51 0.76 8040306 50 26 0.41 0.30 0.59 8050001 51 25 0.27 0.16 0.42 8050002 52 24 0.40 0.33 0.54 8050003 53 27 0.30 0.22 0.46 8060100 54 20 0.36 0.26 0.54 8060201 55 39 0.24 0.17 0.33 8060202 56 43 0.23 0.16 0.32 8060203 57 51 0.25 0.19 0.32 8060204 58 40 0.34 0.27 0.41 8060205 59 45 0.24 0.16 0.31 8060206 60 43 0.32 0.27 0.38 8070100 61 18 0.47 0.39 0.62 8070201 62 57 0.28 0.23 0.34 8070202 63 55 0.25 0.20 0.31 8070203 64 56 0.25 0.18 0.32 8070204 65 41 0.51 0.41 0.61 8070205 66 56 0.26 0.21 0.32

8‐5

8070300 67 33 0.33 0.24 0.43 8080101 68 39 0.35 0.26 0.45 8080102 69 44 0.29 0.22 0.35 8080103 70 37 0.36 0.29 0.45 8080201 71 44 0.33 0.28 0.38 8080202 72 34 0.37 0.27 0.49 8080203 73 50 0.26 0.19 0.32 8080204 74 51 0.28 0.21 0.34 8080205 75 40 0.30 0.23 0.41 8080206 76 50 0.40 0.33 0.48 8090100 77 18 0.59 0.51 0.66 8090201 78 40 0.34 0.27 0.40 8090202 79 11 0.64 0.49 0.90 8090203 80 28 0.58 0.52 0.64 8090301 81 40 0.54 0.44 0.62 8090302 82 42 0.48 0.43 0.54

Figure 8-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Lower Mississippi River Basin

Lower Mississippi River Basin

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Figure 8-3. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Lower Mississippi River Basin

Lower Mississippi River Basin

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Chapter 9

Delivery Ratio used in CEAP Cropland Modeling in the Texas Gulf Basin

8‐5

Delivery Ratio used in CEAP in the Texas Gulf Basin

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nutrients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009) in the Texas Gulf Basin. APEX simulates all of the basic biological, chemical, hydrological, and meteorological processes of farming systems and their interactions. Soil erosion is simulated over time, including wind erosion, sheet and rill erosion. The nitrogen, phosphorus, and carbon cycles are simulated, including chemical transformations in the soil that affect their availability for plant growth or for transport from the field.



Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the deposition is temporary. Eroded soil may deposit in lower spots, flatter lands, deposited at the edge of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary stream

channels during transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National Assessment modeling. The SDR used in this study is a function of the ratio of the time of concentration for the HRU (land uses other than cultivated cropland) or field (cultivated cropland) to the time of concentration for the watershed (8-digit HUC). The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to the time the surface water runoff reaches the outlet of the watershed. It is calculated by summing the overland flow time (the time it takes for flow from the remotest point in the watershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream channels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concentration for the HRU is derived from characteristics of the watershed, the HRU, and the proportion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique delivery ratio within each watershed, as does each HRU. The description of the sediment delivery ratio procedure is provided in Chapter 1.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE developed from Theory) (Williams, 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to determine the amount of sediment that reach the 8-digit watershed outlet from each APEX simulation site. The sediment load from apex simulation sites are aggregated for the 8-digit watershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality effects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimating the SDR for each HRU, the SDR is applied to determine the amount of sediment that reaches the 8-digit watershed outlet.

Sediment delivery ratios were estimated to account for sediment losses or deposition occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated cropland and CRP and non-cropland HRUs in the Texas Gulf Basin (Figure 9-1). The Texas Gulf Basin has a drainage area

8‐5

of 116 million acres. The cultivated cropland and land enrolled in the CRP General Signup is about 15% of the Texas Gulf Basin. A total of 122, 8-digit watersheds are in the Texas Gulf Basin (Figure 9-1). Within each 8-digit watershed, the percent of cultivated cropland and CRP area and non-cultivated cropland area varies widely across the entire basin.

A total of 1573 representative cultivated fields (693 NRI-CEAP cropland points and 880 CRP points) were setup to run using APEX. Twenty-eight out of 112, 8-digit watersheds in the Texas Gulf Basin have no CEAP points; the twenty-eight 8-digit watersheds have zero or fewer than 15% of land cultivated.

Non-cultivated land is distributed over 85% of the Texas Gulf Basin. Within each 8-digit watershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 5,104 HRUs are simulated in SWAT for the Texas Gulf Basin.

Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each cultivated cropland site simulated in an 8-digit watershed and so as for HRU. The number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit watersheds in the Texas Gulf River Basin are shown in Table 9-1 and Figure 9-2. Table 9-2 shows number of HRUs and mean, 10th percentile and 90th percentile of the SDRs estimated for the non-cultivated land HRUs in the 8-digit watersheds in the Texas Gulf Basin. The mean, 10th

and 90th percentile SDRs for the non-cropland HRUs are plotted in Figure 9-3.

In addition to SDR, an enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sediment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the outlet. The enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed outlet. The enrichment ratio is estimated for each APEX

Delivery Ratio used in CEAP in the Texas Gulf Basin

simulation site and SWAT HRUs and it varies from 0.5 to 1.5 (Average 1.0). As sediment is transported from the edge-of-field to the watershed outlet, coarse sediments are deposited first while more of the fine sediment that hold organic particles remain in suspension, thus enriching the organic concentrations delivered to the watershed outlet.


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Figure 9-1. Map of the 8-digit watersheds in the Texas Gulf Basin

Table 9-1. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Texas Gulf Basin

8‐5



DR Points Mean_S DR

10th


12010001 5 0.37 5 0.37 0.36 0.38 12010003 1 0.38 1 0.38 0.38 0.38 12020002 1 0.34 1 0.34 0.34 0.34 12020007 1 0.45 1 0.45 0.45 0.45 12030101 3 0.34 3 0.34 0.33 0.36 12030102 5 0.38 5 0.38 0.36 0.39 12030103 4 0.36 4 0.36 0.35 0.38 12030104 3 0.38 3 0.38 0.38 0.38 12030105 3 0.36 3 0.36 0.35 0.38 12030106 11 0.38 1 0.22 12 0.36 0.26 0.40 12030108 6 0.40 2 0.24 8 0.36 0.23 0.43 12030109 6 0.38 6 0.38 0.34 0.44 12030202 1 0.43 1 0.43 0.43 0.43 12030203 1 0.46 1 0.46 0.46 0.46 12040104 1 0.42 1 0.42 0.42 0.42 12040201 6 0.50 6 0.50 0.44 0.53 12040202 11 0.46 11 0.46 0.41 0.49 12040203 2 0.49 2 0.49 0.49 0.49 12040204 3 0.51 3 0.51 0.51 0.51 12040205 2 0.50 2 0.50 0.49 0.52 12050001 50 0.38 224 0.34 274 0.35 0.22 0.42 12050002 39 0.38 54 0.28 93 0.32 0.20 0.41 12050003 23 0.49 4 0.32 27 0.47 0.31 0.54 12050004 42 0.39 45 0.24 87 0.31 0.22 0.41 12050005 32 0.35 41 0.30 73 0.32 0.21 0.37 12050006 30 0.41 49 0.25 79 0.31 0.22 0.43 12050007 17 0.40 36 0.22 53 0.27 0.20 0.41 12060101 26 0.36 4 0.20 30 0.33 0.21 0.38 12060102 16 0.35 21 0.19 37 0.26 0.18 0.37 12060103 20 0.40 13 0.25 33 0.34 0.24 0.42 12060104 2 0.43 2 0.43 0.43 0.43 12060105 2 0.44 2 0.44 0.41 0.47 12060201 4 0.33 4 0.33 0.32 0.34 12060202 9 0.36 3 0.21 12 0.32 0.20 0.38 12060203 2 0.45 1 0.45 3 0.45 0.45 0.45 12060204 3 0.34 3 0.34 0.33 0.36 12070101 10 0.41 3 0.24 13 0.37 0.22 0.47 12070104 3 0.43 3 0.43 0.40 0.44 12070201 6 0.33 1 0.17 7 0.30 0.17 0.35 12070203 1 0.38 1 0.38 0.38 0.38 12070204 3 0.39 3 0.39 0.38 0.41 12070205 2 0.42 2 0.42 0.39 0.45 12080001 19 0.41 75 0.29 94 0.31 0.24 0.41 12080002 21 0.35 49 0.21 70 0.25 0.20 0.36 12080003 10 0.38 40 0.31 50 0.32 0.21 0.43 12080004 28 0.34 75 0.22 103 0.25 0.18 0.34 12080005 6 0.41 9 0.26 15 0.32 0.25 0.43 12080006 24 0.42 57 0.28 81 0.32 0.25 0.43

8‐5

12080007 5 0.43 6 0.27 11 0.35 0.26 0.45 12080008 4 0.39 8 0.25 12 0.30 0.23 0.40 12090101 10 0.42 17 0.26 27 0.32 0.25 0.43 12090102 2 0.47 2 0.47 0.44 0.50 12090103 5 0.37 3 0.24 8 0.32 0.22 0.39 12090104 2 0.44 2 0.44 0.43 0.44 12090105 10 0.43 4 0.25 14 0.38 0.24 0.46 12090106 8 0.37 1 0.22 9 0.36 0.22 0.46 12090107 4 0.41 1 0.41 5 0.41 0.39 0.43 12090108 4 0.40 2 0.26 6 0.35 0.26 0.41 12090109 1 0.37 1 0.37 0.37 0.37 12090110 1 0.41 1 0.23 2 0.32 0.23 0.41 12090201 1 0.42 1 0.42 0.42 0.42 12090206 1 0.35 1 0.35 0.35 0.35 12090301 3 0.34 3 0.34 0.34 0.34 12090302 1 0.49 1 0.49 0.49 0.49 12090401 5 0.43 5 0.43 0.39 0.46 12090402 1 0.49 1 0.49 0.49 0.49 12100102 4 0.43 4 0.43 0.39 0.47 12100201 1 0.34 1 0.34 0.34 0.34 12100202 2 0.39 2 0.39 0.39 0.39 12100203 2 0.36 2 0.36 0.36 0.36 12100204 1 0.43 1 0.43 0.43 0.43 12100301 1 0.44 1 0.44 0.44 0.44 12100302 3 0.40 3 0.40 0.37 0.41 12100303 2 0.36 2 0.36 0.36 0.36 12100304 6 0.38 6 0.38 0.36 0.40 12100401 5 0.45 5 0.45 0.39 0.46 12100402 5 0.47 5 0.47 0.41 0.49 12100405 1 0.51 1 0.51 0.51 0.51 12100407 8 0.44 8 0.44 0.40 0.48 12110103 1 0.24 1 0.24 0.24 0.24 12110105 3 0.20 3 0.20 0.20 0.21 12110106 5 0.41 1 0.32 6 0.40 0.32 0.45 12110107 1 0.43 1 0.43 0.43 0.43 12110108 1 0.35 1 0.35 0.35 0.35 12110109 2 0.39 2 0.39 0.37 0.41 12110110 1 0.36 1 0.36 0.36 0.36 12110111 4 0.40 1 0.25 5 0.37 0.25 0.42 12110201 1 0.52 1 0.52 0.52 0.52 12110202 1 0.50 1 0.50 0.50 0.50 12110204 2 0.40 1 0.24 3 0.35 0.24 0.41 12110205 12 0.40 12 0.28 24 0.34 0.21 0.43 12110206 6 0.25 6 0.25 0.24 0.26 12110207 1 0.36 2 0.23 3 0.27 0.22 0.36 12110208 29 0.45 1 0.43 30 0.45 0.39 0.47

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Table 9-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Texas Gulf Basin


Mean SDR 10th

Percentile SDR

90th

Percentile SDR

12010001 1 69 0.26 0.22 0.33 12010002 2 43 0.24 0.17 0.35 12010003 3 70 0.28 0.23 0.32 12010004 4 44 0.25 0.19 0.31 12010005 5 45 0.28 0.23 0.34 12020001 6 54 0.24 0.19 0.34 12020002 7 51 0.27 0.21 0.35 12020003 8 49 0.30 0.26 0.38 12020004 9 64 0.26 0.21 0.31 12020005 10 52 0.25 0.19 0.33 12020006 11 55 0.29 0.23 0.36 12020007 12 50 0.34 0.31 0.40 12030101 13 47 0.25 0.18 0.33 12030102 14 57 0.27 0.23 0.33 12030103 15 47 0.27 0.21 0.36 12030104 16 50 0.26 0.21 0.33 12030105 17 57 0.25 0.20 0.31 12030106 18 54 0.28 0.23 0.33 12030107 19 70 0.29 0.24 0.34 12030108 20 50 0.29 0.24 0.35 12030109 21 53 0.25 0.20 0.33 12030201 22 49 0.26 0.20 0.37 12030202 23 45 0.24 0.17 0.35 12030203 24 48 0.34 0.28 0.39 12040101 25 54 0.27 0.21 0.33 12040102 26 48 0.31 0.27 0.37 12040103 27 57 0.28 0.22 0.35 12040104 28 42 0.34 0.28 0.44 12040201 29 46 0.47 0.42 0.55 12040202 30 44 0.40 0.34 0.50 12040203 31 28 0.40 0.34 0.54 12040204 32 47 0.42 0.39 0.47 12040205 33 40 0.43 0.39 0.50 12050001 34 21 0.30 0.21 0.48 12050002 35 17 0.30 0.20 0.59 12050003 36 19 0.40 0.32 0.60 12050004 37 36 0.29 0.22 0.38 12050005 38 19 0.26 0.15 0.43 12050006 39 23 0.30 0.20 0.42 12050007 40 38 0.27 0.21 0.36 12060101 41 35 0.24 0.16 0.34

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12060102 42 45 0.24 0.18 0.31 12060103 43 34 0.29 0.21 0.38 12060104 44 24 0.36 0.29 0.48 12060105 45 41 0.33 0.28 0.40 12060201 46 48 0.22 0.15 0.28 12060202 47 49 0.26 0.21 0.32 12060203 48 29 0.36 0.31 0.42 12060204 49 41 0.25 0.17 0.32 12070101 50 48 0.30 0.25 0.36 12070102 51 53 0.27 0.22 0.34 12070103 52 49 0.24 0.18 0.32 12070104 53 50 0.28 0.21 0.34 12070201 54 48 0.22 0.15 0.30 12070202 55 40 0.27 0.21 0.34 12070203 56 51 0.26 0.21 0.34 12070204 57 45 0.29 0.23 0.36 12070205 58 51 0.27 0.22 0.33 12080001 59 18 0.34 0.24 0.52 12080002 60 34 0.26 0.18 0.38 12080003 61 24 0.31 0.23 0.47 12080004 62 22 0.27 0.16 0.44 12080005 63 20 0.36 0.29 0.61 12080006 64 17 0.38 0.29 0.53 12080007 65 22 0.35 0.28 0.53 12080008 66 39 0.29 0.24 0.36 12090101 67 34 0.32 0.25 0.43 12090102 68 27 0.33 0.27 0.56 12090103 69 31 0.27 0.18 0.41 12090104 70 35 0.28 0.22 0.42 12090105 71 33 0.32 0.27 0.41 12090106 72 46 0.25 0.19 0.33 12090107 73 45 0.33 0.29 0.39 12090108 74 32 0.31 0.25 0.46 12090109 75 43 0.24 0.17 0.34 12090110 76 26 0.29 0.22 0.50 12090201 77 41 0.29 0.24 0.36 12090202 78 29 0.32 0.25 0.43 12090203 79 24 0.31 0.24 0.50 12090204 80 41 0.25 0.17 0.33 12090205 81 48 0.30 0.26 0.34 12090206 82 47 0.25 0.18 0.31 12090301 83 54 0.24 0.18 0.31 12090302 84 45 0.35 0.30 0.39 12090401 85 37 0.33 0.28 0.41 12090402 86 43 0.38 0.33 0.43 12100101 87 54 0.27 0.21 0.33 12100102 88 42 0.28 0.20 0.35 12100201 89 47 0.24 0.17 0.34 12100202 90 62 0.28 0.23 0.32

8‐5

12100203 91 60 0.25 0.20 0.30 12100204 92 74 0.27 0.23 0.32 12100301 93 35 0.38 0.34 0.46 12100302 94 48 0.26 0.22 0.34 12100303 95 53 0.24 0.18 0.29 12100304 96 39 0.28 0.22 0.38 12100401 97 40 0.35 0.29 0.40 12100402 98 36 0.36 0.29 0.43 12100403 99 18 0.52 0.46 0.71 12100404 100 21 0.53 0.47 0.66 12100405 101 35 0.42 0.38 0.48 12100406 102 59 0.29 0.24 0.34 12100407 103 37 0.32 0.26 0.40 12110101 104 43 0.30 0.23 0.40 12110102 105 20 0.32 0.22 0.46 12110103 106 49 0.30 0.25 0.36 12110104 107 49 0.30 0.26 0.37 12110105 108 50 0.25 0.19 0.34 12110106 109 50 0.28 0.24 0.34 12110107 110 36 0.33 0.27 0.41 12110108 111 49 0.26 0.21 0.34 12110109 112 40 0.27 0.21 0.39 12110110 113 47 0.27 0.22 0.35 12110111 114 47 0.26 0.20 0.32 12110201 115 21 0.51 0.45 0.63 12110202 116 24 0.40 0.34 0.55 12110203 117 33 0.57 0.51 0.62 12110204 118 49 0.28 0.21 0.36 12110205 119 39 0.30 0.23 0.40 12110206 120 42 0.31 0.26 0.37 12110207 121 31 0.27 0.21 0.41 12110208 122 35 0.35 0.28 0.42

8‐5

Figure 9-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Texas Gulf Basin

Texas Gulf Basin

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Comment [LH1]: This says lower Mississippi river basin. Should say texas gulf basin?

Figure 9-3. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Texas Gulf Basin

Texas Gulf Basin

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8‐5

Chapter 10

Delivery Ratio used in CEAP Cropland Modeling in the South Atlantic Gulf Basin

10‐1

Delivery Ratio used in CEAP in the South Atlantic Gulf Basin

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nutrients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009) in the South Atlantic Gulf Basin. APEX simulates all of the basic biological, chemical, hydrological, and meteorological processes of farming systems and their interactions. Soil erosion is simulated over time, including wind erosion, sheet and rill erosion. The nitrogen, phosphorus, and carbon cycles are simulated, including chemical transformations in the soil that affect their availability for plant growth or for transport from the field.



Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the deposition is temporary. Eroded soil may deposit in lower spots, flatter lands, deposited at the edge

of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary stream channels during transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National Assessment modeling. The SDR used in this study is a function of the ratio of the time of concentration for the HRU (land uses other than cultivated cropland) or field (cultivated cropland) to the time of concentration for the watershed (8-digit HUC). The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to the time the surface water runoff reaches the outlet of the watershed. It is calculated by summing the overland flow time (the time it takes for flow from the remotest point in the watershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream channels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concentration for the HRU is derived from characteristics of the watershed, the HRU, and the proportion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique delivery ratio within each watershed, as does each HRU. The description of the sediment delivery ratio procedure is provided in Chapter 1.

The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MUSLE developed from Theory) (Williams, 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to determine the amount of sediment that reach the 8-digit watershed outlet from each APEX simulation site. The sediment load from apex simulation sites are aggregated for the 8-digit watershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality effects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimating the SDR for each HRU, the SDR is applied to determine the amount of sediment that reaches the 8-digit watershed outlet.

10‐2

Sediment delivery ratios were estimated to account for sediment losses or deposition occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated cropland and CRP and non-cropland HRUs in the South Atlantic Gulf Basin (Figure 10-1). The South Atlantic Basin has a drainage area of 176 million acres. The cultivated cropland and land enrolled in the CRP General Signup is about 8.9% of the South Atlantic Gulf Basin. A total of 197, 8-digit watersheds are in the South Atlantic Gulf Basin (Figure 10-1). Within each 8-digit watershed, the percent of cultivated cropland and CRP area and non-cultivated cropland area varies widely across the entire basin.

A total of 1505 representative cultivated fields (968 NRI-CEAP cropland points and 537 CRP points) were setup to run using APEX. Forty-seven out of 197, 8-digit watersheds in the South Atlantic Basin have no CEAP points; the forty-seven 8-digit watersheds have zero or fewer than 16.8% of land cultivated.

Non-cultivated land is distributed over 91% of the South Atlantic Gulf Basin. Within each 8-digit watershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 9,040 HRUs are simulated in SWAT for the South Atlantic Gulf Basin.

Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each cultivated cropland site simulated in an 8-digit watershed and so as for HRU. The


number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit watersheds in the South Atlantic Gulf River Basin are shown in Table 10-1 and Figure 10-2. Table 10-2 shows number of HRUs and mean, 10th percentile and 90th percentile of the SDRs estimated for the non-cultivated land HRUs in the 8-digit watersheds in the South Atlantic Basin. The mean, 10th and 90th percentile SDRs for the non-cropland HRUs are plotted in Figure 10-3.

In addition to SDR, an enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sediment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the outlet. The enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed outlet. The enrichment ratio is estimated for each APEX simulation site and SWAT HRUs and it varies from 0.5 to 1.5 (Average 1.0). As sediment is transported from the edge-of-field to the watershed outlet, coarse sediments are deposited first while more of the fine sediment that hold organic particles remain in suspension, thus enriching the organic concentrations delivered to the watershed outlet.


10‐3


Figure 10-1. Map of the 8-digit watersheds in the South Atlantic Gulf Basin

10‐4


Table 10-1. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the South Atlantic Gulf Basin



DR Points Mean_S DR

10th


3010101 3 0.38 1 0.22 4 0.34 0.22 0.41 3010102 2 0.40 2 0.40 0.36 0.45 3010103 4 0.36 4 0.36 0.34 0.38 3010104 5 0.36 5 0.36 0.34 0.37 3010105 3 0.35 3 0.35 0.34 0.35 3010106 1 0.35 2 0.37 3 0.36 0.35 0.37 3010107 13 0.44 13 0.44 0.39 0.49 3010201 20 0.34 20 0.34 0.33 0.36 3010202 29 0.39 1 0.25 30 0.39 0.35 0.46 3010203 28 0.42 1 0.43 29 0.42 0.39 0.49 3010204 36 0.38 3 0.25 39 0.37 0.34 0.41 3010205 71 0.44 71 0.44 0.39 0.47 3020101 5 0.36 1 0.34 6 0.36 0.33 0.38 3020102 10 0.40 1 0.36 11 0.39 0.36 0.41 3020103 21 0.41 21 0.41 0.37 0.46 3020104 9 0.47 9 0.47 0.43 0.54 3020105 5 0.51 1 0.52 6 0.51 0.49 0.52 3020106 3 0.44 3 0.44 0.41 0.45 3020201 18 0.35 4 0.31 22 0.34 0.31 0.40 3020202 14 0.43 14 0.43 0.39 0.50 3020203 20 0.40 4 0.34 24 0.39 0.34 0.44 3020204 8 0.41 8 0.41 0.37 0.45 3030001 2 0.43 2 0.43 0.37 0.48 3030002 8 0.36 8 0.36 0.35 0.37 3030003 1 0.37 1 0.37 0.37 0.37 3030004 17 0.38 1 0.41 18 0.38 0.34 0.45 3030005 6 0.45 1 0.39 7 0.44 0.39 0.49 3030006 16 0.37 16 0.37 0.34 0.39 3030007 6 0.39 6 0.39 0.37 0.42 3040101 11 0.37 11 0.37 0.32 0.47 3040102 2 0.41 1 0.41 3 0.41 0.40 0.41 3040103 1 0.39 1 0.39 0.39 0.39 3040104 4 0.40 2 0.37 6 0.39 0.36 0.47 3040105 16 0.35 5 0.33 21 0.34 0.31 0.36 3040201 31 0.36 14 0.33 45 0.35 0.31 0.40 3040202 13 0.42 6 0.38 19 0.41 0.34 0.47 3040203 34 0.39 1 0.38 35 0.39 0.35 0.46 3040204 44 0.41 2 0.38 46 0.40 0.35 0.46 3040205 22 0.40 13 0.36 35 0.38 0.34 0.42 3040206 13 0.38 3 0.36 16 0.38 0.35 0.44 3040207 1 0.52 1 0.52 0.52 0.52 3050101 1 0.37 1 0.37 0.37 0.37 3050102 1 0.39 1 0.39 0.39 0.39 3050103 1 0.33 1 0.35 2 0.34 0.33 0.35

10‐5


3050104 1 0.35 1 0.33 2 0.34 0.33 0.35 3050105 5 0.38 5 0.37 10 0.37 0.36 0.40 3050108 1 0.36 1 0.36 0.36 0.36 3050109 5 0.33 6 0.32 11 0.32 0.31 0.36 3050110 4 0.38 1 0.37 5 0.38 0.35 0.43 3050111 2 0.39 5 0.37 7 0.37 0.36 0.41 3050112 2 0.37 2 0.37 0.37 0.37 3050201 1 0.45 1 0.45 0.45 0.45 3050202 1 0.46 1 0.46 0.46 0.46 3050203 2 0.35 7 0.35 9 0.35 0.34 0.37 3050204 9 0.40 5 0.36 14 0.38 0.35 0.48 3050205 1 0.45 1 0.45 0.45 0.45 3050206 12 0.40 2 0.35 14 0.39 0.35 0.42 3050207 16 0.38 9 0.37 25 0.38 0.34 0.41 3050208 11 0.39 2 0.39 13 0.39 0.36 0.44 3060101 1 0.40 1 0.40 0.40 0.40 3060102 2 0.40 1 0.37 3 0.39 0.37 0.40 3060103 3 0.36 3 0.36 0.34 0.37 3060106 1 0.34 6 0.37 7 0.37 0.33 0.39 3060107 1 0.39 1 0.39 0.39 0.39 3060108 1 0.32 1 0.32 0.32 0.32 3060109 1 0.35 1 0.35 0.35 0.35 3060201 6 0.34 2 0.32 8 0.34 0.32 0.36 3060202 6 0.37 1 0.33 7 0.37 0.33 0.38 3060203 12 0.35 12 0.35 0.34 0.41 3070101 2 0.32 2 0.32 0.32 0.32 3070102 1 0.34 1 0.34 0.34 0.34 3070103 1 0.31 2 0.34 3 0.33 0.31 0.35 3070104 18 0.35 11 0.32 29 0.34 0.31 0.41 3070105 3 0.35 3 0.34 6 0.35 0.33 0.36 3070106 5 0.39 1 0.35 6 0.39 0.35 0.45 3070107 4 0.35 2 0.32 6 0.34 0.32 0.37 3070201 6 0.37 5 0.35 11 0.36 0.33 0.41 3070202 8 0.39 8 0.39 0.36 0.43 3080102 1 0.35 1 0.35 0.35 0.35 3080103 1 0.47 1 0.47 0.47 0.47 3090204 1 0.38 1 0.38 0.38 0.38 3090205 2 0.40 2 0.40 0.39 0.41 3110103 3 0.38 3 0.38 0.35 0.40 3110202 13 0.33 3 0.32 16 0.33 0.31 0.34 3110203 14 0.37 2 0.34 16 0.36 0.34 0.43 3110204 8 0.35 2 0.35 10 0.35 0.33 0.36 3110205 2 0.37 2 0.37 0.36 0.38 3120001 1 0.35 1 0.35 0.35 0.35 3120002 8 0.37 2 0.36 10 0.37 0.36 0.39 3120003 1 0.34 1 0.34 0.34 0.34 3130002 1 0.32 1 0.32 0.32 0.32 3130003 2 0.33 2 0.33 0.31 0.36 3130004 16 0.36 8 0.34 24 0.35 0.33 0.37 3130005 3 0.32 3 0.32 0.32 0.32 3130006 15 0.34 4 0.33 19 0.34 0.33 0.36

10‐6


3130007 7 0.35 1 0.36 8 0.35 0.33 0.38 3130008 8 0.37 3 0.37 11 0.37 0.35 0.39 3130009 10 0.38 2 0.34 12 0.37 0.34 0.46 3130010 12 0.38 12 0.38 0.36 0.39 3130012 5 0.35 8 0.33 13 0.34 0.32 0.37 3140103 3 0.35 10 0.33 13 0.33 0.32 0.36 3140104 1 0.36 1 0.36 0.36 0.36 3140201 16 0.36 16 0.34 32 0.35 0.33 0.38 3140202 5 0.32 12 0.32 17 0.32 0.31 0.35 3140203 4 0.35 19 0.35 23 0.35 0.34 0.36 3140301 2 0.38 2 0.38 0.38 0.38 3140302 2 0.35 1 0.35 3 0.35 0.34 0.36 3140303 1 0.36 1 0.36 0.36 0.36 3140304 1 0.37 1 0.37 0.37 0.37 3140305 4 0.36 4 0.36 0.35 0.36 3150101 2 0.49 2 0.49 0.45 0.52 3150103 1 0.43 1 0.43 0.43 0.43 3150104 1 0.36 1 0.36 0.36 0.36 3150105 8 0.43 8 0.43 0.35 0.52 3150106 7 0.34 1 0.30 8 0.33 0.30 0.40 3150107 3 0.37 3 0.37 0.37 0.37 3150110 1 0.35 1 0.35 0.35 0.35 3150201 8 0.32 8 0.32 0.30 0.34 3150202 3 0.32 3 0.32 0.31 0.33 3150203 22 0.35 22 0.35 0.33 0.37 3150204 2 0.41 2 0.41 0.40 0.41 3160101 8 0.39 8 0.37 16 0.38 0.35 0.41 3160102 10 0.41 5 0.38 15 0.40 0.37 0.44 3160103 3 0.36 4 0.38 7 0.37 0.36 0.40 3160104 6 0.42 33 0.39 39 0.39 0.35 0.44 3160105 3 0.44 4 0.43 7 0.43 0.41 0.45 3160106 11 0.40 26 0.39 37 0.39 0.37 0.42 3160108 3 0.44 40 0.36 43 0.36 0.32 0.40 3160109 1 0.42 1 0.42 0.42 0.42 3160111 1 0.32 4 0.32 5 0.32 0.32 0.33 3160112 3 0.41 3 0.41 0.41 0.41 3160113 8 0.36 8 0.36 0.32 0.44 3160201 2 0.38 2 0.38 0.37 0.39 3160202 6 0.39 6 0.39 0.36 0.40 3160203 1 0.33 1 0.33 0.33 0.33 3160205 4 0.40 4 0.40 0.38 0.41 3170001 1 0.37 1 0.37 0.37 0.37 3170002 2 0.34 2 0.34 0.34 0.34 3170003 1 0.39 1 0.39 0.39 0.39 3170004 2 0.35 19 0.33 21 0.33 0.31 0.38 3170005 4 0.33 4 0.33 0.31 0.36 3170006 3 0.42 4 0.38 7 0.40 0.35 0.44 3170007 7 0.35 7 0.35 0.33 0.38 3170008 2 0.37 2 0.37 0.37 0.37 3170009 3 0.35 3 0.35 0.34 0.36 3180001 22 0.35 22 0.35 0.32 0.39

10‐7


3180002 2 0.37 8 0.35 10 0.35 0.32 0.38 3180003 1 0.41 5 0.37 6 0.38 0.35 0.41 3180004 7 0.35 7 0.35 0.32 0.39 3180005 1 0.33 12 0.33 13 0.33 0.30 0.35

Table 10-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the South Atlantic Gulf Basin HUC Subbasin Number_of non-

cropland HRUs simulated within SWAT

Mean SDR 10th

Percentile SDR

90th

Percentile SDR

3010101 1 63 0.21 0.15 0.26 3010102 2 54 0.23 0.16 0.29 3010103 3 53 0.23 0.17 0.27 3010104 4 56 0.23 0.17 0.29 3010105 5 58 0.22 0.15 0.28 3010106 6 45 0.23 0.17 0.33 3010107 7 42 0.28 0.21 0.37 3010201 8 50 0.22 0.13 0.27 3010202 9 50 0.26 0.20 0.32 3010203 10 39 0.29 0.22 0.37 3010204 11 47 0.24 0.18 0.30 3010205 12 44 0.32 0.23 0.39 3020101 13 50 0.23 0.18 0.31 3020102 14 49 0.26 0.19 0.33 3020103 15 44 0.26 0.18 0.33 3020104 16 38 0.39 0.32 0.47 3020105 17 37 0.40 0.31 0.49 3020106 18 45 0.36 0.33 0.41 3020201 19 40 0.22 0.14 0.33 3020202 20 39 0.29 0.22 0.39 3020203 21 56 0.23 0.17 0.30 3020204 22 44 0.29 0.24 0.39 3030001 23 43 0.28 0.23 0.37 3030002 24 67 0.22 0.18 0.28 3030003 25 71 0.20 0.14 0.26 3030004 26 42 0.25 0.18 0.35 3030005 27 44 0.33 0.27 0.42 3030006 28 41 0.25 0.17 0.34 3030007 29 41 0.24 0.16 0.32 3040101 30 56 0.21 0.16 0.27 3040102 31 86 0.27 0.23 0.32 3040103 32 73 0.25 0.20 0.30 3040104 33 54 0.25 0.20 0.33 3040105 34 77 0.21 0.16 0.25 3040201 35 35 0.23 0.13 0.34

10‐8


3040202 36 45 0.25 0.17 0.32 3040203 37 37 0.25 0.17 0.33 3040204 38 43 0.25 0.17 0.33 3040205 39 39 0.26 0.19 0.34 3040206 40 43 0.24 0.16 0.32 3040207 41 48 0.37 0.34 0.43 3050101 42 60 0.21 0.15 0.27 3050102 43 75 0.24 0.20 0.29 3050103 44 57 0.22 0.16 0.30 3050104 45 49 0.22 0.14 0.29 3050105 46 51 0.25 0.19 0.28 3050106 47 51 0.25 0.19 0.29 3050107 48 61 0.24 0.18 0.29 3050108 49 63 0.23 0.17 0.28 3050109 50 39 0.22 0.13 0.31 3050110 51 57 0.23 0.17 0.29 3050111 52 45 0.26 0.19 0.31 3050112 53 37 0.25 0.16 0.33 3050201 54 48 0.27 0.21 0.35 3050202 55 42 0.29 0.22 0.37 3050203 56 47 0.24 0.17 0.30 3050204 57 53 0.23 0.18 0.27 3050205 58 46 0.30 0.26 0.37 3050206 59 35 0.26 0.20 0.37 3050207 60 40 0.25 0.17 0.30 3050208 61 44 0.26 0.19 0.33 3060101 62 66 0.25 0.21 0.29 3060102 63 50 0.23 0.17 0.31 3060103 64 52 0.22 0.15 0.30 3060104 65 69 0.20 0.15 0.26 3060105 66 60 0.21 0.15 0.26 3060106 67 36 0.22 0.12 0.34 3060107 68 55 0.23 0.16 0.29 3060108 69 52 0.20 0.12 0.28 3060109 70 49 0.24 0.16 0.31 3060201 71 31 0.24 0.14 0.40 3060202 72 39 0.25 0.16 0.35 3060203 73 47 0.23 0.15 0.30 3060204 74 51 0.33 0.29 0.37 3070101 75 35 0.20 0.12 0.41 3070102 76 30 0.23 0.12 0.36 3070103 77 38 0.20 0.12 0.34 3070104 78 29 0.23 0.12 0.37 3070105 79 46 0.22 0.14 0.30 3070106 80 44 0.25 0.17 0.33 3070107 81 30 0.23 0.13 0.41 3070201 82 36 0.25 0.16 0.34 3070202 83 49 0.25 0.19 0.30

10‐9


3070203 84 44 0.38 0.34 0.45 3070204 85 50 0.23 0.17 0.30 3070205 86 37 0.32 0.28 0.40 3080101 87 54 0.23 0.17 0.29 3080102 88 54 0.24 0.18 0.31 3080103 89 50 0.28 0.24 0.33 3080201 90 35 0.44 0.40 0.52 3080202 91 25 0.46 0.41 0.57 3080203 92 27 0.47 0.37 0.57 3090101 93 59 0.22 0.17 0.29 3090102 94 21 0.42 0.36 0.58 3090103 95 30 0.30 0.23 0.44 3090201 96 1 0.95 0.95 0.95 3090202 97 39 0.34 0.29 0.42 3090203 98 2 0.79 0.75 0.83 3090204 99 36 0.34 0.30 0.43 3090205 100 40 0.34 0.26 0.41 3100101 101 55 0.23 0.18 0.29 3100102 102 38 0.34 0.29 0.40 3100201 103 35 0.37 0.31 0.45 3100202 104 38 0.30 0.23 0.38 3100203 105 29 0.31 0.23 0.43 3100204 106 44 0.30 0.25 0.35 3100205 107 39 0.31 0.25 0.39 3100206 108 41 0.35 0.30 0.44 3100207 109 46 0.30 0.23 0.35 3100208 110 47 0.24 0.16 0.30 3110101 111 43 0.32 0.24 0.43 3110102 112 48 0.35 0.31 0.42 3110103 113 39 0.26 0.19 0.38 3110201 114 42 0.22 0.14 0.35 3110202 115 33 0.22 0.11 0.34 3110203 116 32 0.24 0.14 0.40 3110204 117 39 0.23 0.14 0.32 3110205 118 36 0.28 0.20 0.37 3110206 119 51 0.24 0.17 0.29 3120001 120 40 0.26 0.17 0.35 3120002 121 33 0.27 0.19 0.36 3120003 122 34 0.24 0.15 0.36 3130001 123 56 0.22 0.16 0.28 3130002 124 45 0.21 0.13 0.28 3130003 125 42 0.22 0.13 0.29 3130004 126 36 0.24 0.16 0.32 3130005 127 50 0.21 0.13 0.27 3130006 128 30 0.24 0.14 0.38 3130007 129 37 0.24 0.16 0.35 3130008 130 43 0.25 0.18 0.32 3130009 131 38 0.25 0.18 0.34

10‐10


3130010 132 38 0.26 0.17 0.34 3130011 133 40 0.26 0.17 0.37 3130012 134 54 0.22 0.15 0.28 3130013 135 35 0.31 0.25 0.45 3130014 136 1 0.95 0.95 0.95 3140101 137 52 0.28 0.20 0.33 3140102 138 47 0.28 0.22 0.34 3140103 139 43 0.22 0.14 0.31 3140104 140 43 0.25 0.18 0.33 3140105 141 41 0.43 0.40 0.49 3140106 142 47 0.24 0.17 0.30 3140107 143 42 0.43 0.39 0.49 3140201 144 31 0.24 0.16 0.44 3140202 145 39 0.21 0.13 0.36 3140203 146 53 0.23 0.18 0.27 3140301 147 53 0.23 0.17 0.29 3140302 148 58 0.22 0.16 0.26 3140303 149 41 0.23 0.16 0.33 3140304 150 51 0.24 0.18 0.30 3140305 151 41 0.23 0.14 0.30 3150101 152 67 0.26 0.21 0.33 3150102 153 59 0.27 0.22 0.34 3150103 154 71 0.22 0.16 0.28 3150104 155 58 0.23 0.17 0.29 3150105 156 53 0.24 0.17 0.32 3150106 157 49 0.20 0.10 0.28 3150107 158 45 0.24 0.17 0.33 3150108 159 67 0.21 0.14 0.27 3150109 160 52 0.23 0.16 0.31 3150110 161 59 0.23 0.16 0.29 3150201 162 30 0.24 0.15 0.41 3150202 163 45 0.20 0.11 0.28 3150203 164 29 0.25 0.16 0.41 3150204 165 52 0.24 0.17 0.29 3160101 166 33 0.26 0.19 0.42 3160102 167 49 0.24 0.19 0.35 3160103 168 50 0.22 0.15 0.29 3160104 169 53 0.23 0.17 0.33 3160105 170 44 0.27 0.20 0.35 3160106 171 39 0.26 0.18 0.34 3160107 172 52 0.21 0.13 0.26 3160108 173 50 0.22 0.15 0.28 3160109 174 54 0.24 0.19 0.31 3160110 175 56 0.22 0.16 0.30 3160111 176 55 0.20 0.13 0.29 3160112 177 48 0.27 0.21 0.31 3160113 178 48 0.23 0.17 0.31 3160201 179 31 0.26 0.17 0.40

10‐11


3160202 180 50 0.24 0.18 0.29 3160203 181 40 0.24 0.17 0.35 3160204 182 44 0.25 0.17 0.33 3160205 183 48 0.27 0.21 0.32 3170001 184 58 0.25 0.20 0.30 3170002 185 50 0.22 0.15 0.28 3170003 186 44 0.27 0.20 0.37 3170004 187 52 0.22 0.15 0.32 3170005 188 42 0.22 0.13 0.31 3170006 189 51 0.29 0.23 0.35 3170007 190 51 0.22 0.15 0.29 3170008 191 54 0.21 0.14 0.28 3170009 192 52 0.25 0.18 0.31 3180001 193 46 0.23 0.17 0.37 3180002 194 42 0.23 0.16 0.33 3180003 195 64 0.23 0.19 0.31 3180004 196 60 0.23 0.17 0.30 3180005 197 59 0.20 0.14 0.29

10‐12


Sedi

men

t Del

iver

y R

a tio

Se

dim

ent D

eliv

ery

Rat

io

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

3010

101

3010

105

3010

101

3010

104

3010

202

3010

107

3020

101

3010

203

Figure 10-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the South Atlantic Gulf Basin

South Atlantic Gulf Basin 1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2 Mean SDR 10th Percentile SDR 90th Percentile SDR 0.1

0.0

HUC8

Figure 10-3. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the South Atlantic Gulf Basin

South Atlantic Gulf Basin

1.0 Mean SDR 10th Percentile SDR 90th Percentile SDR 0.9

HUC8

3020

105

3020

101

3020

203

3020

104

3030

003

3020

201

3030

007

3020

204

3040

104

3030

003

3040

203

3030

006

3040

207

3040

102

3050

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3040

105

3050

108

3040

203

3050

112

3040

206

3050

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3050

208

3050

102

3050

105

3060

104

3050

110

3060

108

3050

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3050

204

3070

103

3050

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3070

107

3060

102

3070

204

3060

107

3080

103

3060

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3090

101

3070

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3090

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3070

104

3100

101

3100

203

3070

107

3100

207

3080

102

3110

103

3110

204

3090

205

3120

002

3130

003

3130

007

3130

011

3140

101

3140

105

3110

203

3120

001

3130

002

3130

005

3130

008

3130

012

3140

201

3140

202

3140

301

3140

303

3140

304

3150

102

3150

103

3150

106

3150

106

3150

110

3150

201

3150

204

3150

204

3160

104

3160

103

3160

108

3160

106

3160

112

3160

111

3160

203

3160

201

3170

002

3160

205

3170

006

3170

003

3180

001

3170

006

3180

005

3170

009

3180

003

10‐13


10‐14

11-1

Chapter 11

Delivery Ratio used in CEAP Cropland Modeling in the Pacific Northwest River

Basin

Delivery Ratio used in CEAP in the Pacific Northwest River Basin

11-2

The APEX model is a field-scale, daily time-step model that simulates weather, farming operations, crop growth and yield, and the movement of water, soil, carbon, nutrients, sediment, and pesticides. The APEX model was used also to simulate the effects of conservation practices at the field scale (Williams and Izaurralde, 2006; Gassman et al. 2009) in the Pacific Northwest River Basin. APEX simulates all of the basic biological, chemical, hydrological, and meteorological processes of farming systems and their interactions. Soil erosion is simulated over time, including wind erosion, sheet and rill erosion. The nitrogen, phosphorus, and carbon cycles are simulated, including chemical transformations in the soil that affect their availability for plant growth or for transport from the field.

While the APEX model was used for simulating the cultivated cropland and the SWAT model was used to simulate the non-cultivated cropland in the 8-digit watersheds of the river basin. SWAT is a physical process model with a daily time step (Arnold and Fohrer 2005; Arnold et al. 1998; Gassman et al. 2007). In SWAT, each 8-digit watershed is divided into multiple Hydrologic Response Units (HRUs) that have homogeneous land use, soil, and slope. SWAT is used to simulate the fate and transport of water, sediment, nutrients, and pesticides from various non-cropland HRUs as described in Chapter 1. The hydrologic cycle in the model is divided into two parts. The land phase of the hydrologic cycle, or upland processes, simulates the amount of water, sediment, nutrients, and pesticides delivered from the non-cropland HRUs to the outlet of each watershed. The routing phase of the hydrologic cycle, or channel processes, simulates the movement of water, sediment, nutrients, and pesticides from the outlet of the upstream watershed through the main channel network to the watershed outlet. Not all of the soil that erodes from a field or HRUs ends up in the watershed outlet. Most of the soil eroded gets deposited on the way although the deposition is temporary. Eroded soil may deposit in lower spots, flatter lands, deposited at the edge of the field and sometimes settles at the bottom of the channel. Hence, a SDR was used to account for deposition in ditches, floodplains, and tributary stream channels during transit from the edge of the field or HRUs to the 8-digit watershed outlet in the CEAP National Assessment modeling. The SDR used in this study is a function of the ratio of the time of concentration for the HRU (land uses other than cultivated cropland) or

field (cultivated cropland) to the time of concentration for the watershed (8-digit HUC). The time of concentration for the watershed is the time from when a surface water runoff event occurs at the most distant point in the watershed to the time the surface water runoff reaches the outlet of the watershed. It is calculated by summing the overland flow time (the time it takes for flow from the remotest point in the watershed to reach the channel) and the channel flow time (the time it takes for flow in the upstream channels to reach the outlet). The time of concentration for the field is derived from APEX. The time of concentration for the HRU is derived from characteristics of the watershed, the HRU, and the proportion of total acres represented by the HRU. Consequently, each cultivated cropland sample point has a unique delivery ratio within each watershed, as does each HRU. The description of the sediment delivery ratio procedure is provided in Chapter 1. The APEX model simulates the edge of sediment yield using a variation of MUSLE called MUST (MU

SLE developed from Theory) (Williams, 1995) as described in Chapter 1. After estimating the sediment load from each APEX simulation site, the delivery ratio is applied to determine the amount of sediment that reaches the 8-digit watershed outlet from each APEX simulation site. The sediment load from apex simulation sites are aggregated for the 8-digit watershed and integrated into the SWAT model at each 8-digit watershed to estimate the water quality effects of conservation practices. In SWAT, the sediment yield for the non-cropland HRUs are estimated using the MUSLE as described in Chapter 1. After estimating the SDR for each HRU, the SDR is applied to determine the amount of sediment that reaches the 8-digit watershed outlet.

Sediment delivery ratios were estimated to account for sediment losses or deposition occurring from edge-of-field or HRUs to the 8-digit watershed outlet for each APEX simulation site in the cultivated cropland and CRP and non-cropland HRUs in the Pacific Northwest River Basin (Figure 11-1). The Pacific Northwest River Basin has a drainage area of 327 million acres. The cultivated cropland and land enrolled in the CRP General Signup is about 29 percent of the Pacific Northwest River Basin. A total of 218, 8-digit watersheds are in the Pacific Northwest River Basin (Figure 11-1). Within each 8-digit watershed, the percent of cultivated cropland and CRP area and non-cultivated cropland area varies widely across the entire


11-3

basin. A total of 1748 representative cultivated fields (922 NRI-CEAP cropland points and 826 CRP points) were setup to run using APEX. One hundred and twenty-four out of 218, 8-digit watersheds in the Pacific Northwest have no CEAP points; the 124 8-digit watersheds have zero or fewer than 10% percentage cultivated cropland, except 2 of them having 14% and 19% cultivated cropland, respectively. Non-cultivated land is distributed over 91.5 percent of the Pacific Northwest River Basin. Within each 8-digit watershed, non-cultivated land uses such as pasture, range, hay, horticulture, forest deciduous, forest mixed, forest evergreen, urban, urban construction, barren land wetland and water are simulated as HRUs in SWAT. A total of 9,143 HRUs are simulated in SWAT for the Pacific Northwest River Basin. Each NRI-CEAP point and CRP point is unique; therefore, sediment yield and delivery ratio also vary for each cultivated cropland site simulated in an 8-digit watershed and so as for HRU. The number of CEAP sample points, and mean, 10th percentile and 90th percentile of the delivery ratios of the APEX simulation sites in the 8-digit watersheds in the Pacific Northwest River Basin are shown in Table 11-1 and Figure 11-2. Table 11-2 shows number of HRUs and mean, 10th percentile and 90th percentile of the SDRs estimated for the non-cultivated land HRUs in the 8-digit watersheds in the Pacific Northwest River Basin (Figure 11-1). The mean, 10th and 90th percentile

SDRs for the non-cropland HRUs are plotted in Figure 11-3. In addition to SDR, an enrichment ratio was used to simulate organic nitrogen, organic phosphorus, and sediment-attached pesticide transport in ditches, floodplains, and tributary stream channels during transit from the edge of the field to the outlet. The enrichment ratio was defined as the organic nitrogen, organic phosphorus, and sediment attached pesticide concentration from the edge-of-field divided by the concentration at the 8-digit watershed outlet. The enrichment ratio is estimated for each APEX simulation site and SWAT HRUs and it varies from 0.5 to 1.5 (Average 1.0). As sediment is transported from the edge-of-field to the watershed outlet, coarse sediments are deposited first while more of the fine sediment that hold organic particles remain in suspension, thus enriching the organic concentrations delivered to the watershed outlet. A separate delivery ratio is used to simulate the transport of nitrate nitrogen, soluble phosphorus, and soluble pesticides. In general, the proportion of soluble nutrients and pesticides delivered to rivers and streams is higher than the proportion attached to sediments because they are not subject to sediment deposition.


11-4

Figure 11-1. Map of the 8-digit watersheds in the Pacific North West River Basin


11-5

Table 11-1. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Pacific Northwest River Basin.


Points Mean_SDR Points Mean_S

DR Points Mean_SDR

10th percentile

90th percentile

17010104 5 0.53 2 0.38 7 0.49 0.37 0.60 17010203 3 0.38 3 0.38 0.38 0.38 17010204 1 0.50 1 0.50 0.50 0.50 17010208 8 0.45 8 0.45 0.41 0.50 17010210 3 0.44 3 0.44 0.43 0.45 17010212 1 0.36 1 0.36 0.36 0.36 17010303 1 0.47 3 0.35 4 0.38 0.35 0.47 17010304 1 0.35 1 0.35 0.35 0.35 17010305 5 0.44 5 0.44 0.38 0.47 17010306 16 0.43 8 0.27 24 0.38 0.21 0.48 17010307 3 0.44 7 0.24 10 0.30 0.22 0.50 17020001 3 0.52 1 0.24 4 0.45 0.24 0.65 17020003 1 0.50 1 0.50 0.50 0.50 17020004 1 0.21 1 0.21 0.21 0.21 17020005 3 0.41 18 0.26 21 0.29 0.24 0.41 17020006 3 0.43 3 0.43 0.40 0.46 17020010 3 0.40 10 0.25 13 0.29 0.23 0.41 17020012 6 0.39 21 0.26 27 0.29 0.24 0.41 17020013 26 0.35 12 0.27 38 0.32 0.26 0.37 17020014 5 0.39 1 0.25 6 0.37 0.25 0.41 17020015 26 0.38 34 0.24 60 0.30 0.21 0.39 17020016 35 0.41 36 0.24 71 0.32 0.21 0.43 17030001 3 0.41 3 0.41 0.40 0.41 17030003 8 0.39 11 0.21 19 0.29 0.19 0.41 17040104 2 0.42 13 0.40 15 0.40 0.33 0.46 17040105 1 0.38 1 0.38 0.38 0.38 17040201 39 0.41 11 0.36 50 0.40 0.35 0.46 17040202 2 0.40 2 0.40 0.39 0.40 17040203 9 0.48 12 0.45 21 0.46 0.42 0.50 17040204 36 0.49 33 0.44 69 0.46 0.43 0.58 17040205 8 0.41 8 0.41 0.39 0.42 17040206 25 0.41 45 0.36 70 0.38 0.34 0.44 17040207 1 0.42 3 0.37 4 0.38 0.36 0.42 17040208 11 0.39 78 0.37 89 0.37 0.34 0.41 17040209 51 0.38 45 0.33 96 0.36 0.32 0.39 17040210 9 0.39 12 0.40 21 0.40 0.36 0.47 17040211 8 0.45 8 0.45 0.41 0.48


11-6

17040212 38 0.43 1 0.42 39 0.43 0.40 0.44 17040213 1 0.42 2 0.40 3 0.41 0.40 0.42 17040215 1 0.60 1 0.60 0.60 0.60 17040218 1 0.47 1 0.47 0.47 0.47 17040219 5 0.45 5 0.45 0.43 0.48 17040220 4 0.43 6 0.42 10 0.43 0.40 0.44 17040221 5 0.47 2 0.44 7 0.46 0.44 0.50 17050101 5 0.39 1 0.39 6 0.39 0.35 0.44 17050103 9 0.39 9 0.39 0.35 0.44 17050114 29 0.43 29 0.43 0.39 0.53 17050115 14 0.53 14 0.53 0.45 0.60 17050117 1 0.47 1 0.47 0.47 0.47 17050122 18 0.45 18 0.45 0.41 0.52 17050124 5 0.43 4 0.39 9 0.41 0.38 0.47 17050201 1 0.55 1 0.28 2 0.41 0.28 0.55 17050203 1 0.44 1 0.44 0.44 0.44 17060103 7 0.50 14 0.34 21 0.39 0.31 0.51 17060104 6 0.43 3 0.38 9 0.41 0.38 0.45 17060105 2 0.41 2 0.41 0.40 0.43 17060106 1 0.47 1 0.47 0.47 0.47 17060107 39 0.41 76 0.23 115 0.29 0.22 0.41 17060108 25 0.36 10 0.24 35 0.32 0.19 0.41 17060109 13 0.36 11 0.22 24 0.30 0.19 0.40 17060110 4 0.37 39 0.22 43 0.23 0.19 0.32 17060209 1 0.40 1 0.40 0.40 0.40 17060305 4 0.43 4 0.43 0.40 0.52 17060306 24 0.40 16 0.35 40 0.38 0.32 0.42 17070101 20 0.41 26 0.28 46 0.34 0.24 0.44 17070102 33 0.42 51 0.21 84 0.29 0.19 0.44 17070103 23 0.37 28 0.30 51 0.33 0.28 0.38 17070104 19 0.40 27 0.29 46 0.34 0.28 0.42 17070105 21 0.44 3 0.39 24 0.44 0.39 0.53 17070106 3 0.42 5 0.26 8 0.32 0.25 0.43 17070204 37 0.36 50 0.30 87 0.33 0.28 0.39 17070306 10 0.37 17 0.33 27 0.35 0.29 0.43 17070307 1 0.47 3 0.30 4 0.34 0.28 0.47 17080001 1 0.65 1 0.65 0.65 0.65 17090003 41 0.41 41 0.41 0.38 0.46 17090005 3 0.46 3 0.46 0.44 0.47 17090006 5 0.48 5 0.48 0.47 0.49 17090007 14 0.46 14 0.46 0.42 0.49 17090008 23 0.45 23 0.45 0.40 0.52 17090009 3 0.53 3 0.53 0.47 0.62 17090010 10 0.45 10 0.45 0.40 0.56 17090012 3 0.52 3 0.52 0.50 0.55 17100303 2 0.32 2 0.32 0.30 0.34


11-7

17100308 1 0.51 1 0.51 0.51 0.51 17100309 1 0.49 1 0.49 0.49 0.49 17110001 1 0.68 1 0.68 0.68 0.68 17110002 1 0.54 1 0.54 0.54 0.54 17110004 7 0.58 7 0.58 0.52 0.62 17110007 3 0.60 3 0.60 0.60 0.60 17110009 1 0.50 1 0.50 0.50 0.50 17110011 1 0.48 1 0.48 0.48 0.48 17110014 1 0.48 1 0.48 0.48 0.48 17110019 10 0.48 10 0.48 0.41 0.57 17120002 1 0.34 1 0.34 0.34 0.34

Figure 11-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at simulation sites) estimated for cultivated simulation sites within APEX for the 8-digit watersheds in the Pacific Northwest River Basin

Pacific Northwest River Basin

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1701

0104

1701

0208

1701

0303

1701

0306

1702

0003

1702

0006

1702

0013

1702

0016

1704

0104

1704

0202

1704

0205

1704

0208

1704

0211

1704

0215

1704

0220

1705

0103

1705

0117

1705

0201

1706

0104

1706

0107

1706

0110

1706

0306

1707

0103

1707

0106

1707

0307

1709

0005

1709

0008

1709

0012

1710

0309

1711

0004

1711

0011

1712

0002

HUC8

Sed

imen

t Del

iver

y R

atio



11-8

Table 11-2. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Pacific Northwest River Basin


Mean SDR 10th Percentile SDR

90th Percentile SDR

17010101 1 55 0.206 0.133 0.265 17010102 2 43 0.216 0.125 0.322 17010103 3 28 0.224 0.107 0.397 17010104 4 35 0.234 0.134 0.348 17010105 5 24 0.256 0.150 0.543 17010201 6 47 0.187 0.078 0.317 17010202 7 50 0.199 0.109 0.291 17010203 8 55 0.179 0.087 0.272 17010204 9 58 0.173 0.092 0.239 17010205 10 53 0.175 0.083 0.225 17010206 11 40 0.208 0.104 0.325 17010207 12 42 0.191 0.078 0.300 17010208 13 42 0.220 0.110 0.330 17010209 14 48 0.173 0.073 0.284 17010210 15 42 0.209 0.107 0.313 17010211 16 33 0.217 0.101 0.354 17010212 17 53 0.179 0.080 0.231 17010213 18 59 0.166 0.074 0.251 17010214 19 45 0.224 0.137 0.312 17010215 20 43 0.199 0.099 0.309 17010216 21 46 0.190 0.090 0.292 17010301 22 31 0.209 0.095 0.353 17010302 23 27 0.244 0.130 0.462 17010303 24 38 0.237 0.137 0.333 17010304 25 55 0.179 0.085 0.246 17010305 26 25 0.227 0.104 0.485 17010306 27 31 0.245 0.139 0.392 17010307 28 37 0.211 0.098 0.324 17010308 29 37 0.245 0.152 0.351 17020001 30 47 0.240 0.168 0.330 17020002 31 39 0.258 0.172 0.359 17020003 32 39 0.205 0.100 0.310 17020004 33 49 0.205 0.118 0.276 17020005 34 44 0.210 0.104 0.290 17020006 35 51 0.210 0.132 0.281 17020007 36 37 0.261 0.174 0.371 17020008 37 51 0.188 0.096 0.286 17020009 38 51 0.191 0.094 0.277


11-9

17020010 39 42 0.219 0.110 0.286 17020011 40 47 0.198 0.111 0.279 17020012 41 29 0.216 0.083 0.381 17020013 42 26 0.207 0.080 0.394 17020014 43 26 0.204 0.090 0.501 17020015 44 24 0.218 0.079 0.465 17020016 45 26 0.221 0.101 0.446 17030001 46 50 0.195 0.106 0.281 17030002 47 44 0.202 0.102 0.317 17030003 48 43 0.191 0.083 0.322 17040101 49 52 0.184 0.085 0.265 17040102 50 40 0.214 0.108 0.326 17040103 51 53 0.191 0.103 0.264 17040104 52 45 0.193 0.085 0.282 17040105 53 47 0.204 0.104 0.278 17040201 54 22 0.241 0.101 0.420 17040202 55 44 0.198 0.099 0.270 17040203 56 34 0.248 0.158 0.341 17040204 57 33 0.244 0.138 0.361 17040205 58 38 0.223 0.122 0.316 17040206 59 30 0.227 0.103 0.360 17040207 60 41 0.206 0.096 0.300 17040208 61 33 0.208 0.082 0.340 17040209 62 25 0.210 0.085 0.434 17040210 63 39 0.199 0.093 0.303 17040211 64 35 0.217 0.099 0.311 17040212 65 34 0.225 0.114 0.314 17040213 66 56 0.193 0.114 0.253 17040214 67 34 0.222 0.122 0.335 17040215 68 32 0.244 0.149 0.366 17040216 69 35 0.231 0.124 0.347 17040217 70 48 0.201 0.099 0.301 17040218 71 43 0.185 0.066 0.263 17040219 72 46 0.214 0.144 0.265 17040220 73 40 0.209 0.108 0.284 17040221 74 35 0.244 0.157 0.384 17050101 75 45 0.207 0.111 0.290 17050102 76 52 0.215 0.176 0.277 17050103 77 50 0.210 0.164 0.271 17050104 78 55 0.206 0.119 0.277 17050105 79 56 0.188 0.088 0.272 17050106 80 27 0.234 0.106 0.386 17050107 81 46 0.228 0.126 0.291 17050108 82 41 0.220 0.123 0.307 17050109 83 41 0.229 0.127 0.332 17050110 84 49 0.198 0.115 0.294 17050111 85 43 0.218 0.121 0.327


11-10

17050112 86 38 0.233 0.133 0.376 17050113 87 54 0.184 0.092 0.270 17050114 88 46 0.213 0.120 0.287 17050115 89 21 0.360 0.268 0.554 17050116 90 53 0.190 0.099 0.264 17050117 91 37 0.230 0.134 0.342 17050118 92 28 0.297 0.197 0.429 17050119 93 31 0.246 0.115 0.390 17050120 94 51 0.201 0.112 0.270 17050121 95 28 0.247 0.134 0.466 17050122 96 50 0.224 0.170 0.300 17050123 97 45 0.195 0.097 0.285 17050124 98 50 0.202 0.108 0.265 17050201 99 50 0.229 0.143 0.282 17050202 100 42 0.206 0.096 0.287 17050203 101 39 0.219 0.118 0.319 17060101 102 36 0.233 0.120 0.376 17060102 103 43 0.209 0.107 0.288 17060103 104 35 0.264 0.156 0.353 17060104 105 47 0.203 0.099 0.264 17060105 106 33 0.234 0.114 0.320 17060106 107 50 0.208 0.126 0.291 17060107 108 28 0.243 0.107 0.355 17060108 109 20 0.244 0.098 0.540 17060109 110 19 0.257 0.091 0.411 17060110 111 22 0.233 0.093 0.491 17060201 112 54 0.177 0.085 0.235 17060202 113 49 0.208 0.118 0.317 17060203 114 59 0.209 0.138 0.274 17060204 115 60 0.189 0.100 0.253 17060205 116 53 0.200 0.118 0.272 17060206 117 55 0.192 0.102 0.262 17060207 118 54 0.181 0.097 0.288 17060208 119 52 0.183 0.090 0.295 17060209 120 54 0.180 0.084 0.272 17060210 121 46 0.214 0.126 0.309 17060301 122 34 0.223 0.105 0.317 17060302 123 31 0.249 0.140 0.330 17060303 124 38 0.205 0.088 0.295 17060304 125 20 0.326 0.199 0.631 17060305 126 33 0.220 0.098 0.330 17060306 127 31 0.239 0.126 0.351 17060307 128 49 0.192 0.086 0.243 17060308 129 49 0.197 0.103 0.273 17070101 130 30 0.240 0.119 0.376 17070102 131 24 0.249 0.112 0.430 17070103 132 36 0.213 0.096 0.327


11-11

17070104 133 28 0.239 0.104 0.363 17070105 134 41 0.231 0.144 0.330 17070106 135 40 0.213 0.112 0.319 17070201 136 53 0.194 0.102 0.264 17070202 137 55 0.185 0.097 0.265 17070203 138 38 0.211 0.107 0.349 17070204 139 54 0.180 0.076 0.243 17070301 140 47 0.224 0.143 0.305 17070302 141 29 0.208 0.101 0.320 17070303 142 41 0.197 0.105 0.267 17070304 143 46 0.202 0.108 0.294 17070305 144 32 0.195 0.097 0.299 17070306 145 52 0.186 0.087 0.263 17070307 146 29 0.253 0.128 0.434 17080001 147 46 0.276 0.212 0.326 17080002 148 47 0.204 0.121 0.276 17080003 149 45 0.239 0.171 0.305 17080004 150 42 0.219 0.129 0.329 17080005 151 45 0.213 0.143 0.304 17080006 152 49 0.235 0.169 0.301 17090001 153 51 0.193 0.111 0.288 17090002 154 44 0.206 0.119 0.298 17090003 155 56 0.184 0.118 0.254 17090004 156 44 0.199 0.114 0.298 17090005 157 40 0.210 0.133 0.339 17090006 158 53 0.205 0.133 0.270 17090007 159 49 0.242 0.183 0.324 17090008 160 47 0.209 0.125 0.319 17090009 161 49 0.240 0.177 0.344 17090010 162 50 0.215 0.132 0.308 17090011 163 45 0.196 0.106 0.316 17090012 164 42 0.262 0.196 0.351 17100101 165 44 0.215 0.128 0.313 17100102 166 50 0.213 0.118 0.293 17100103 167 45 0.204 0.119 0.306 17100104 168 45 0.230 0.156 0.307 17100105 169 38 0.283 0.212 0.389 17100106 170 42 0.205 0.101 0.302 17100201 171 19 0.338 0.227 0.545 17100202 172 55 0.179 0.094 0.268 17100203 173 53 0.210 0.138 0.294 17100204 174 52 0.212 0.143 0.297 17100205 175 44 0.211 0.123 0.316 17100206 176 50 0.183 0.090 0.271 17100207 177 33 0.273 0.165 0.410 17100301 178 45 0.195 0.105 0.287 17100302 179 52 0.185 0.100 0.271


11-12

17100303 180 49 0.182 0.089 0.270 17100304 181 51 0.208 0.121 0.312 17100305 182 52 0.207 0.138 0.275 17100307 183 48 0.199 0.113 0.282 17100308 184 55 0.216 0.149 0.280 17100309 185 46 0.203 0.115 0.325 17100310 186 39 0.206 0.111 0.339 17100311 187 46 0.193 0.098 0.292 17100312 188 45 0.206 0.116 0.326 17110001 189 29 0.385 0.317 0.547 17110002 190 50 0.239 0.182 0.310 17110003 191 1 0.950 0.950 0.950 17110004 192 45 0.235 0.174 0.338 17110005 193 49 0.211 0.127 0.292 17110006 194 38 0.214 0.113 0.393 17110007 195 45 0.257 0.186 0.352 17110008 196 42 0.220 0.135 0.348 17110009 197 41 0.218 0.135 0.362 17110010 198 46 0.217 0.154 0.312 17110011 199 39 0.229 0.149 0.348 17110012 200 42 0.239 0.150 0.356 17110013 201 43 0.218 0.134 0.316 17110014 202 46 0.233 0.175 0.309 17110015 203 47 0.236 0.181 0.300 17110016 204 28 0.355 0.272 0.532 17110017 205 33 0.240 0.142 0.459 17110018 206 41 0.257 0.168 0.354 17110019 207 53 0.228 0.173 0.289 17110020 208 43 0.247 0.181 0.336 17110021 209 36 0.246 0.162 0.485 17120001 210 40 0.256 0.160 0.348 17120002 211 58 0.190 0.110 0.254 17120003 212 36 0.225 0.118 0.341 17120004 213 50 0.197 0.110 0.294 17120005 214 52 0.179 0.075 0.278 17120006 215 41 0.195 0.080 0.301 17120007 216 45 0.193 0.088 0.311 17120008 217 44 0.181 0.080 0.315 17120009 218 44 0.177 0.067 0.315


11-13

Figure 11-3. Mean and percentiles of sediment delivery ratio (sediment delivered at 8-digit watershed outlet by sediment yield at HRUs) estimated for non-cultivated land HRUs within SWAT for the 8-digit watersheds in the Pacific Northwest River Basin

Pacific Northwest River Basin

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documentation on delivery ratio used for ceap cropland ...delivery ratio used in ceap in the upper...

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